Muni Intermediate Duration -- Converted by SEC Publisher, created by BCL Technologies Inc., for SEC Filing

UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

FORM N-Q

QUARTERLY SCHEDULE OF PORTFOLIO HOLDINGS OF REGISTERED
MANAGEMENT INVESTMENT COMPANY

Investment Company Act file number 811-21348

Name of Fund: BlackRock Muni Intermediate Duration Fund, Inc. (MUI)

Fund Address: 100 Bellevue Parkway, Wilmington, DE 19809

Name and address of agent for service: Donald C. Burke, Chief Executive Officer, BlackRock Muni
Intermediate Duration Fund, Inc., 800 Scudders Mill Road, Plainsboro, NJ, 08536. Mailing
address: P.O. Box 9011, Princeton, NJ, 08543-9011

Registrant’s telephone number, including area code: (800) 882-0052, Option 4

Date of fiscal year end: 05/31/2009

Date of reporting period: 06/01/2008 – 08/31/2008

Item 1 – Schedule of Investments

BlackRock Muni Intermediate Duration Fund, Inc.             
Schedule of Investments August 31, 2008 (Unaudited)    (Percentages shown are based on Net Assets) 
 
            Par     
State    Municipal Bonds        (000)    Value 
 
 
 
 
Alabama - 2.9%    Jefferson County, Alabama, Limited Obligation School Warrants, Series A,         
    5.50%, 1/01/21        $ 5,500    $ 4,840,055 
    Jefferson County, Alabama, Limited Obligation School Warrants, Series A,         
    5.25%, 1/01/23        6,500    5,720,195 
    Tuscaloosa, Alabama, Special Care Facilities Financing Authority, Residential         
    Care Facility Revenue Bonds (Capstone Village, Inc. Project), Series A,         
    5.625%, 8/01/25        6,600    5,289,636 
               
                15,849,886 
 
 
 
 
Arizona - 2.9%    Maricopa County, Arizona, IDA, Education Revenue Bonds (Arizona Charter         
    Schools Project 1), Series A, 6.625%, 7/01/20        2,820    2,529,371 
    Navajo County, Arizona, IDA, IDR (Stone Container Corporation Project), AMT,         
    7.20%, 6/01/27        3,000    2,709,360 
    Pima County, Arizona, IDA, Education Revenue Bonds (Arizona Charter Schools         
    Project), Series C, 6.70%, 7/01/21        985    998,908 
    Pima County, Arizona, IDA, Education Revenue Bonds (Arizona Charter Schools         
    Project), Series K, 6.375%, 7/01/13 (a)        820    941,754 
    Pima County, Arizona, IDA, Education Revenue Bonds (Arizona Charter Schools         
    Project), Series K, 6.375%, 7/01/31        930    905,922 
    Salt River Project, Arizona, Agriculture Improvement and Power District,         
    Electric System Revenue Bonds, Series A, 5%, 1/01/25        4,000    4,194,440 
    Vistancia Community Facilities District, Arizona, GO, 5%, 7/15/14    3,630    3,637,115 
           
                15,916,870 
 
 
 
 
Arkansas - 0.7%    Conway, Arkansas, Public Facilities Board, Capital Improvement Revenue         
    Refunding Bonds (Hendrix College Projects), Series B, 5%, 10/01/26    3,755    3,704,270 
 
 
 
California - 18.5%    Antelope Valley, California, Health Care District Revenue Bonds, VRDN,         
    Series A, 5.25%, 9/01/17        8,000    7,611,200 
    California Pollution Control Financing Authority, PCR, Refunding (Pacific Gas         
    & Electric), AMT, Series A, 5.35%, 12/01/16 (b)        17,730    17,913,505 
    California Pollution Control Financing Authority, Solid Waste Disposal Revenue         
    Bonds (Republic Services Inc. Project), AMT, Series B, 5.25%, 6/01/23    750    694,830 
    California Pollution Control Financing Authority, Solid Waste Disposal Revenue         
    Bonds (Waste Management Inc. Project), AMT, Series A-2, 5.40%, 4/01/25    1,240    1,091,250 
    California State Department of Water Resources, Power Supply Revenue         
    Bonds, Series A, 5.375%, 5/01/12 (a)        5,000    5,559,900 
    California State, GO, 5.50%, 4/01/14 (a)        14,795    16,527,346 
    California State, GO, 5.50%, 4/01/28        15    15,436 
 
 
 
 
Portfolio Abbreviations             
 
 
 

To simplify the listings of portfolio holdings in the Schedule of Investments, the names of many of the securities have been abbreviated according to the list below.

AMT    Alternative Minimum Tax (subject to)    IDA    Industrial Development Authority 
COP    Certificates of Participation    IDR    Industrial Development Revenue Bonds 
EDA    Economic Development Authority    PCR    Pollution Control Revenue Bonds 
EDR    Economic Development Revenue Bonds    S/F    Single-Family 
GO    General Obligation Bonds    VRDN    Variable Rate Demand Notes 
HFA    Housing Finance Agency         

1

BlackRock Muni Intermediate Duration Fund, Inc.             
Schedule of Investments August 31, 2008 (Unaudited)    (Percentages shown are based on Net Assets) 
 
            Par     
State    Municipal Bonds        (000)    Value 
 
 
 
 
    California State, GO, Refunding, 5.25%, 2/01/27 (b)        $ 5,000   $  5,084,500 
    California State Public Works Board, Lease Revenue Bonds (Department of         
    Corrections), Series C, 5.50%, 6/01/20        10,000    10,544,000 
    California Statewide Communities Development Authority, Health Facility         
    Revenue Bonds (Memorial Health Services), Series A, 6%, 10/01/23    2,500    2,590,175 
    Elk Grove, California, Poppy Ridge Community Facilities District Number 3,         
    Special Tax Bonds, Series 1, 6%, 9/01/08 (a)        2,400    2,424,504 
    Golden State Tobacco Securitization Corporation of California, Tobacco         
    Settlement Revenue Refunding Bonds, Senior Series A-1, 5%, 6/01/15    5,000    4,923,700 
    Los Angeles, California, Regional Airports Improvement Corporation, Facilities         
    Lease Revenue Refunding Bonds (LAXFUEL Corporation -             
    Los Angeles International Airport), AMT, 5.50%, 1/01/32 (c)    1,435    1,412,643 
    Los Angeles County, California, Metropolitan Transportation Authority, Sales         
    Tax Revenue Refunding Bonds, Proposition C, VRDN, Second Senior Series A,         
    7.50%, 7/01/20 (b)(d)        8,000    8,000,000 
    Rowland, California, Unified School District, GO (Election of 2000), Series B,         
    5.25%, 8/01/27 (e)        1,515    1,561,238 
    Sacramento, California, Special Tax (North Natomas Community Facilities),         
    Series 4-C, 5.60%, 9/01/20        585    585,234 
    Sacramento, California, Special Tax (North Natomas Community Facilities),         
    Series 4-C, 5.75%, 9/01/22        1,715    1,706,854 
    Sacramento, California, Special Tax (North Natomas Community Facilities),         
    Series 4-C, 5.90%, 9/01/23        500    501,500 
    Sacramento, California, Special Tax (North Natomas Community Facilities),         
    Series 4-C, 6%, 9/01/28        2,990    2,990,000 
    Sacramento County, California, Airport System Revenue Bonds, Senior         
    Series A, 5%, 7/01/28 (e)        1,695    1,730,561 
    Southern California HFA, S/F Mortgage Revenue Bonds, AMT, Series A, 5.80%,         
    12/01/49 (f)(g)(h)        3,910    3,935,571 
    Tustin, California, Unified School District, Senior Lien Special Tax Bonds         
    (Community Facilities District Number 97-1), Series A, 5%, 9/01/32 (e)    2,610    2,616,551 
           
                100,020,498 
 
 
 
 
Colorado - 2.8%    Colorado Educational and Cultural Facilities Authority, Revenue Refunding         
    Bonds (National Jewish Federation Bond Program Project), VRDN, Series A-8,         
    2.25%, 9/01/35 (d)        3,050    3,050,000 
    Elk Valley, Colorado, Public Improvement Revenue Bonds (Public Improvement         
    Fee), Series A, 7.10%, 9/01/14        700    726,243 
    Montrose, Colorado, Memorial Hospital, Revenue Bonds, 6.375%, 12/01/23    2,250    2,336,400 
    Plaza Metropolitan District Number 1, Colorado, Tax Allocation Revenue Bonds         
    (Public Improvement Fees), 7.50%, 12/01/15        7,500    7,980,300 
    Southlands Metropolitan District Number 1, Colorado, GO, 6.75%,         
    12/01/14 (a)        1,000    1,153,470 
               
                15,246,413 
 
 
 
 
Connecticut -    Connecticut State Development Authority, Airport Facility Revenue Bonds         
1.3%    (Learjet Inc. Project), AMT, 7.95%, 4/01/26        1,160    1,232,036 

2

BlackRock Muni Intermediate Duration Fund, Inc.             
Schedule of Investments August 31, 2008 (Unaudited)    (Percentages shown are based on Net Assets) 
 
            Par     
State    Municipal Bonds        (000)    Value 
 
 
 
 
    Connecticut State Development Authority, PCR, Refunding (Connecticut Light         
    and Power Company), Series A, 5.85%, 9/01/28        $ 6,000    $ 5,975,460 
           
 
                7,207,496 
 
 
 
 
Florida - 5.4%    Florida Housing Finance Corporation, Homeowner Mortgage Revenue Bonds,         
    AMT, Series 6, 4.70%, 7/01/37        5,380    4,344,565 
    Harbor Bay, Florida, Community Development District, Capital Improvement         
    Special Assessment Bonds, 6.75%, 5/01/34        2,860    2,798,253 
    Highlands County, Florida, Health Facilities Authority, Hospital Revenue         
    Refunding Bonds (Adventist Health System), Series G, 5.125%, 11/15/32    1,000    954,050 
    Miami-Dade County, Florida, Aviation Revenue Refunding Bonds (Miami         
    International Airport), AMT, 5.75%, 10/01/19 (i)        5,500    5,558,025 
    Midtown Miami, Florida, Community Development District, Special Assessment         
    Revenue Bonds, Series A, 6%, 5/01/24        3,465    3,171,826 
    Midtown Miami, Florida, Community Development District, Special Assessment         
    Revenue Bonds, Series B, 6.50%, 5/01/37        1,975    1,821,404 
    Orlando, Florida, Urban Community Development District, Capital         
    Improvement Special Assessment Bonds, 6%, 5/01/20        820    761,903 
    Panther Trace Community Development District II, Florida, Special Assessment         
    Revenue Bonds, 5.125%, 11/01/13        2,255    2,075,750 
    Portofino Shores, Florida, Community Development District, Special         
    Assessment Bonds, Series A, 6.40%, 5/01/34        1,085    1,097,185 
    South Lake County, Florida, Hospital District Revenue Bonds (South Lake         
    Hospital Inc.), 6.625%, 10/01/23        2,390    2,484,381 
    Sterling Hill Community Development District, Florida, Capital Improvement         
    Revenue Refunding Bonds, Series B, 5.50%, 11/01/10        185    182,904 
    University of Florida Research Foundation Inc., Capital Improvement Revenue         
    Bonds, 5.125%, 9/01/33 (c)        4,000    4,001,360 
               
                29,251,606 
 
 
 
 
Georgia - 0.3%    Atlanta, Georgia, Tax Allocation Bonds (Atlantic Station Project), 7.90%,         
    12/01/11 (a)        1,500    1,766,475 
 
 
 
 
Idaho - 0.8%    Boise City, Idaho, COP, AMT, 5.50%, 9/01/25 (i)        4,000    3,922,120 
    Idaho Housing and Finance Association, S/F Mortgage Revenue Bonds, AMT,         
    Series F-2, 5.85%, 7/01/15 (j)        260    266,804 
               
                4,188,924 
 
 
 
 
Illinois - 5.7%    Chicago, Illinois, O'Hare International Airport, General Airport Revenue Bonds,         
    Third Lien, AMT, Series B-2, 6%, 1/01/29 (k)        2,510    2,535,978 
    Chicago, Illinois, O'Hare International Airport, General Airport Revenue         
    Refunding Bonds, Third Lien, AMT, Series A-2, 5.75%, 1/01/19 (e)    2,550    2,609,670 
    Du Page and Will Counties, Illinois, Community School District Number 204         
    (Indian Prairie), GO, 5.25%, 12/30/22 (i)        8,650    9,195,988 
    Hodgkins, Illinois, Environmental Improvement Revenue Bonds (Metro Biosolids         
    Management LLC Project), AMT, 5.90%, 11/01/17        6,000    6,002,400 
    Illinois, Development Finance Authority Revenue Bonds (Community         
    Rehabilitation Providers Facilities), Series A, 6.625%, 7/01/32    6,930    7,144,276 

3

BlackRock Muni Intermediate Duration Fund, Inc.             
Schedule of Investments August 31, 2008 (Unaudited)    (Percentages shown are based on Net Assets) 
 
            Par     
State    Municipal Bonds        (000)    Value 
 
 
 
 
    Illinois State Finance Authority Revenue Bonds (Landing At Plymouth Place         
    Project), Series A, 6%, 5/15/25        $ 1,800    $ 1,665,738 
    Village of Wheeling, Illinois, Revenue Bonds (North Milwaukee/Lake-Cook Tax         
    Increment Financing (TIF) Redevelopment Project), 6%, 1/01/25    1,580    1,428,873 
           
                30,582,923 
 
 
 
 
Indiana - 0.4%    Jasper County, Indiana, PCR, Refunding (Northern Indiana Public Service),         
    Series C, 5.85%, 4/01/19 (b)        2,000    2,001,120 
 
 
 
 
Louisiana - 2.6%    Louisiana Public Facilities Authority Revenue Bonds (Nineteenth Judicial         
    District Court Building Project), 5.50%, 6/01/41 (i)        2,000    1,998,600 
    Louisiana Public Facilities Authority Revenue Bonds (University of New Orleans         
    Research and Technology Foundation, Inc. - Student Housing Project), 5.25%,         
    3/01/26 (b)        6,965    7,110,917 
    Port New Orleans, Louisiana, IDR, Refunding (Continental Grain Company         
    Project), 6.50%, 1/01/17        5,000    4,934,750 
               
                14,044,267 
 
 
 
 
Maine - 0.3%    Portland, Maine, Housing Development Corporation, Senior Living Revenue         
    Bonds (Avesta Housing Development Corporation Project), Series A,         
    6%, 2/01/34        1,965    1,881,055 
 
 
 
 
Maryland - 0.1%    Maryland State Industrial Development Financing Authority, EDR (Our Lady of         
    Good Counsel School), Series A, 6%, 5/01/35        500    486,985 
 
 
 
 
Massachusetts -    Massachusetts Bay Transportation Authority, Sales Tax Revenue Refunding         
1.5%    Bonds, Senior Series A, 5%, 7/01/12 (a)        4,560    4,953,756 
    Massachusetts State Development Finance Agency, Resource Recovery         
    Revenue Bonds (Ogden Haverhill Associates), AMT, Series B, 5.35%, 12/01/15    1,210    1,164,843 
    Massachusetts State Development Finance Agency, Resource Recovery         
    Revenue Bonds (Ogden Haverhill Associates), AMT, Series B, 5.50%, 12/01/19    2,000    1,926,880 
           
                8,045,479 
 
 
 
 
Michigan - 1.4%    Macomb County, Michigan, Hospital Finance Authority, Hospital Revenue         
    Bonds (Mount Clemens General Hospital), Series B, 5.875%, 11/15/13 (a)    2,325    2,617,648 
    Michigan State Hospital Finance Authority, Revenue Refunding Bonds         
    (Oakwood Obligated Group), Series A, 6%, 4/01/22        4,795    4,933,432 
               
                7,551,080 
 
 
 
 
Minnesota - 1.0%    Minneapolis and Saint Paul, Minnesota, Housing and Redevelopment Authority,         
    Health Care System Revenue Bonds (Group Health Plan Inc. Project), 6%,         
    12/01/19        1,000    1,023,830 
    Minneapolis and Saint Paul, Minnesota, Housing and Redevelopment Authority,         
    Health Care System Revenue Bonds (Group Health Plan Inc. Project), 6%,         
    12/01/21        2,545    2,589,385 
    Minnesota State Municipal Power Agency, Electric Revenue Bonds, Series A,         
    5.25%, 10/01/24        2,000    2,029,020 
               
                5,642,235 
 
 
 
 

4

BlackRock Muni Intermediate Duration Fund, Inc.             
Schedule of Investments August 31, 2008 (Unaudited)    (Percentages shown are based on Net Assets) 
 
            Par     
State    Municipal Bonds        (000)    Value 
 
 
 
 
Mississippi - 1.4%    Mississippi Business Finance Corporation, Mississippi, PCR, Refunding (System         
    Energy Resources Inc. Project), 5.875%, 4/01/22        $ 5,000    $ 4,829,650 
    Mississippi Business Finance Corporation, Mississippi, PCR, Refunding (System         
    Energy Resources Inc. Project), 5.90%, 5/01/22        2,910    2,814,406 
               
                7,644,056 
 
 
 
 
Nebraska - 1.3%    Public Power Generation Agency, Nebraska, Revenue Bonds (Whelan Energy         
    Center Unit 2), Series A, 5%, 1/01/37 (c)        7,000    6,813,380 
 
 
 
 
Nevada - 0.4%    Clark County, Nevada, Improvement District Number 142, Special Assessment         
    Bonds, 6.375%, 8/01/23        2,195    2,060,381 
 
 
 
 
New Jersey -    Garden State Preservation Trust of New Jersey, Open Space and Farmland         
12.5%    Preservation Revenue Bonds, Series A, 5.80%, 11/01/21 (e)    3,635    4,096,645 
    Garden State Preservation Trust of New Jersey, Open Space and Farmland         
    Preservation Revenue Bonds, Series A, 5.80%, 11/01/23 (e)    5,050    5,629,942 
    New Jersey EDA, Cigarette Tax Revenue Bonds, 5.75%, 6/15/29    9,810    9,307,924 
    New Jersey EDA, Motor Vehicle Surcharge Revenue Bonds, Series A, 5.25%,         
    7/01/33 (b)        17,900    18,168,142 
    New Jersey EDA, Special Facility Revenue Bonds (Continental Airlines Inc.         
    Project), AMT, 6.625%, 9/15/12        5,540    5,118,406 
    New Jersey EDA, Water Facilities Revenue Refunding Bonds (American Water),         
    AMT, Series B, 5.125%, 4/01/22 (c)        5,000    4,725,850 
    New Jersey State Housing and Mortgage Finance Agency, S/F Housing Revenue         
    Bonds, AMT, Series X, 5.10%, 10/01/23        4,500    4,303,485 
    New Jersey State Transportation Trust Fund Authority, Transportation System         
    Revenue Bonds, Series D, 5%, 6/15/18 (c)        4,215    4,472,621 
    New Jersey State Transportation Trust Fund Authority, Transportation System         
    Revenue Bonds, Series D, 5%, 6/15/19 (e)        11,120    11,752,172 
               
                67,575,187 
 
 
 
 
New Mexico -    New Mexico Finance Authority, Senior Lien State Transportation Revenue         
1.9%    Bonds, Series A, 5.125%, 6/15/18 (b)        9,520    10,137,372 
 
 
 
 
New York - 26.2%    Dutchess County, New York, IDA, Civic Facility Revenue Bonds (Saint Francis         
    Hospital), Series B, 7.25%, 3/01/19        1,030    1,083,467 
    Metropolitan Transportation Authority, New York, Revenue Refunding Bonds,         
    Series A, 5%, 11/15/25 (i)        4,100    4,112,054 
    New York City, New York, City IDA, Special Facility Revenue Bonds         
    (Continental Airlines Inc. Project), AMT, 8.375%, 11/01/16    3,500    3,374,210 
    New York City, New York, City Transitional Finance Authority, Building Aid         
    Revenue Bonds, Series S-1, 5%, 7/15/24 (i)        2,500    2,570,500 
    New York City, New York, City Transitional Finance Authority, Building Aid         
    Revenue Refunding Bonds, Series S-1, 5%, 1/15/34        3,625    3,635,041 
    New York City, New York, GO, Refunding, Series B, 5.75%, 8/01/15    5,000    5,474,050 
    New York City, New York, GO, Series D1, 5.125%, 12/01/26    4,615    4,753,496 
    New York City, New York, IDA, Civic Facility Revenue Bonds (Special Needs         
    Facilities Pooled Program), Series C-1, 6.80%, 7/01/19        2,055    2,033,690 

5

BlackRock Muni Intermediate Duration Fund, Inc.             
Schedule of Investments August 31, 2008 (Unaudited)    (Percentages shown are based on Net Assets) 
 
            Par     
State    Municipal Bonds        (000)    Value 
 
 
 
 
    New York City, New York, Sales Tax Asset Receivable Corporation Revenue         
    Bonds, Series A, 5%, 10/15/20 (b)        $ 9,070     $9,502,911 
    New York State Dormitory Authority, Lease Revenue Refunding Bonds (Court         
    Facilities), Series A, 5.25%, 5/15/12        5,580    6,034,491 
    New York State Dormitory Authority, Non-State Supported Debt, Lease         
    Revenue Bonds (Municipal Health Facilities Improvement Program),         
    Sub-Series 2-4, 5%, 1/15/27        6,900    6,956,166 
    New York State Dormitory Authority, Non-State Supported Debt, Revenue         
    Refunding Bonds (Mount Sinai-NYU Medical Center Health System), Series A,         
    6.625%, 7/01/10 (a)        4,615    5,020,843 
    New York State Dormitory Authority, Non-State Supported Debt, Revenue         
    Refunding Bonds (Mount Sinai-NYU Medical Center Health System), Series A,         
    6.625%, 7/01/18        2,385    2,472,577 
    New York State Dormitory Authority, Non-State Supported Debt, Revenue         
    Refunding Bonds (Mount Sinai-NYU Medical Center Health System), Series A,         
    6.625%, 7/01/19        1,330    1,376,231 
    New York State Dormitory Authority Revenue Bonds (North Shore - Long Island         
    Jewish Health System), 5%, 5/01/12        1,000    1,054,040 
    New York State Dormitory Authority Revenue Bonds (School Districts Financing         
    Program), Series D, 5.25%, 10/01/23 (b)        9,540    10,029,497 
    New York State Environmental Facilities Corporation, State Personal Income         
    Tax Revenue Bonds, Series A, 5.25%, 12/15/14 (a)(i)        7,380    8,322,500 
    New York State Thruway Authority, Local Highway and Bridge Service         
    Contract, Revenue Refunding Bonds, 5.50%, 4/01/17        60    64,939 
    New York State Urban Development Corporation, Correctional and Youth         
    Facilities Services, Revenue Refunding Bonds, Series A, 5.50%, 1/01/17    10,825    11,451,551 
    New York State Urban Development Corporation, Personal Income Tax         
    Revenue Bonds (State Facilities), Series A-1, 5.25%, 3/15/34 (i)    10,000    10,214,100 
    Port Authority of New York and New Jersey, Consolidated Revenue Refunding         
    Bonds, 153rd Series, 5%, 7/15/24        2,010    2,110,601 
    Port Authority of New York and New Jersey, Senior Consolidated Revenue         
    Bonds, AMT, 131st Series, 5%, 12/15/17 (l)        5,000    5,107,050 
    Tobacco Settlement Financing Corporation of New York Revenue Bonds, Series         
    A-1, 5.25%, 6/01/22 (c)        6,510    6,761,612 
    Tobacco Settlement Financing Corporation of New York Revenue Bonds, Series         
    C-1, 5.50%, 6/01/20 (i)        9,750    10,299,218 
    Tobacco Settlement Financing Corporation of New York Revenue Bonds, Series         
    C-1, 5.50%, 6/01/21        7,000    7,375,760 
    Tobacco Settlement Financing Corporation of New York Revenue Bonds, Series         
    C-1, 5.50%, 6/01/22        10,000    10,492,900 
               
                141,683,495 
 
 
 
 
North Carolina -    Gaston County, North Carolina, Industrial Facilities and Pollution Control         
2.2%    Financing Authority, Revenue Bonds (National Gypsum Company Project),         
    AMT, 5.75%, 8/01/35        3,105    2,418,422 

6

BlackRock Muni Intermediate Duration Fund, Inc.             
Schedule of Investments August 31, 2008 (Unaudited)    (Percentages shown are based on Net Assets) 
 
            Par     
State    Municipal Bonds        (000)    Value 
 
 
 
 
    North Carolina Medical Care Commission, Health Care Facilities, First         
    Mortgage Revenue Refunding Bonds (Presbyterian Homes Project), 7%,         
    10/01/10 (a)        $ 6,000   $  6,630,240 
    North Carolina Municipal Power Agency Number 1, Catawba Electric Revenue         
    Bonds, Series A, 5.25%, 1/01/20 (b)        2,700    2,758,563 
               
                11,807,225 
 
 
 
 
Ohio - 1.0%    Buckeye Tobacco Settlement Financing Authority, Ohio, Tobacco Settlement         
    Asset-Backed Bonds, Series A-2, 6.50%, 6/01/47        4,820    4,286,956 
    Port of Greater Cincinnati Development Authority, Ohio, Special Assessment         
    Revenue Bonds (Cooperative Public Parking Infrastructure Project), 6.30%,         
    2/15/24        1,280    1,294,054 
               
                5,581,010 
 
 
 
 
Pennsylvania -    Montgomery County, Pennsylvania, IDA, Revenue Bonds (Whitemarsh         
9.1%    Continuing Care Project), 6%, 2/01/21        3,500    3,289,755 
    Pennsylvania Economic Development Financing Authority, Exempt Facilities         
    Revenue Bonds (National Gypsum Company), AMT, Series A, 6.25%, 11/01/27    7,710    6,632,528 
    Philadelphia, Pennsylvania, Airport Revenue Bonds (Philadelphia Airport         
    System), AMT, Series A, 5%, 6/15/20 (e)        2,895    2,821,785 
    Philadelphia, Pennsylvania, Airport Revenue Refunding Bonds (Philadelphia         
    Airport System), AMT, Series B, 5%, 6/15/19 (e)        3,905    3,831,625 
    Philadelphia, Pennsylvania, Gas Works Revenue Refunding Bonds, 1975         
    General Ordinance, 17th Series, 5.375%, 7/01/22 (e)        7,490    7,928,465 
    Pittsburgh, Pennsylvania, GO, Refunding, Series B, 5.25%, 9/01/17 (e)    9,630    10,539,457 
    Pittsburgh, Pennsylvania, GO, Series C, 5.25%, 9/01/18 (e)    6,430    6,971,406 
    Sayre, Pennsylvania, Health Care Facilities Authority, Revenue Refunding         
    Bonds (Guthrie Healthcare System), Series A, 6.25%, 12/01/11 (a)    4,615    5,170,969 
    Sayre, Pennsylvania, Health Care Facilities Authority, Revenue Refunding         
    Bonds (Guthrie Healthcare System), Series A, 6.25%, 12/01/15    455    484,611 
    Sayre, Pennsylvania, Health Care Facilities Authority, Revenue Refunding         
    Bonds (Guthrie Healthcare System), Series A, 6.25%, 12/01/16    785    832,163 
    Sayre, Pennsylvania, Health Care Facilities Authority, Revenue Refunding         
    Bonds (Guthrie Healthcare System), Series A, 6.25%, 12/01/18    385    404,192 
           
                48,906,956 
 
 
 
 
South Carolina -    Georgetown County, South Carolina, Pollution Control Facilities, Revenue         
2.3%    Refunding Bonds (International Paper Company Project), Series A, 5.125%,         
    2/01/12        8,000    7,952,640 
    Medical University Hospital Authority, South Carolina, Hospital Facilities         
    Revenue Refunding Bonds, Series A, 5.25%, 8/15/23 (b)(j)        4,250    4,365,770 
               
                12,318,410 
 
 
 
 
South Dakota -    Educational Enhancement Funding Corporation, South Dakota, Series B, 6.50%,         
0.4%    6/01/32        2,200    2,161,852 
 
 
 
 
Tennessee - 3.6%    Johnson City, Tennessee, Health and Educational Facilities Board, Retirement         
    Facility Revenue Bonds (Appalachian Christian Village Project), Series A, 6%,         
    2/15/19        1,800    1,710,144 

7

BlackRock Muni Intermediate Duration Fund, Inc.             
Schedule of Investments August 31, 2008 (Unaudited)    (Percentages shown are based on Net Assets) 
 
            Par     
State    Municipal Bonds        (000)    Value 
 
 
 
 
    Memphis-Shelby County, Tennessee, Airport Authority, Airport Revenue Bonds,         
    AMT, Series A, 5.50%, 3/01/17 (e)        $ 2,005    $ 2,030,303 
    Shelby County, Tennessee, Health, Educational and Housing Facility Board,         
    Hospital Revenue Refunding Bonds (Methodist Healthcare), 6%, 9/01/12 (a)    6,000    6,733,140 
    Shelby County, Tennessee, Health, Educational and Housing Facility Board,         
    Hospital Revenue Refunding Bonds (Methodist Healthcare), 6.25%, 9/01/12 (a)    3,500    3,960,635 
    Shelby County, Tennessee, Health, Educational & Housing Facilities Board         
    Revenue Bonds (Germantown Village), Series A, 6.75%, 12/01/18    3,550    3,344,384 
    Shelby County, Tennessee, Health, Educational and Housing Facilities Board         
    Revenue Bonds (Germantown Village), Series A, 7%, 12/01/23    1,450    1,401,106 
           
                19,179,712 
 
 
 
 
Texas - 13.4%    Austin, Texas, Convention Center Revenue Bonds (Convention Enterprises         
    Inc.), First Tier, Series A, 6.375%, 1/01/11 (a)        5,945    6,411,564 
    Austin, Texas, Convention Center Revenue Bonds (Convention Enterprises         
    Inc.), First Tier, Series A, 6.70%, 1/01/11 (a)        10,260    11,232,648 
    Bexar County, Texas, Health Facilities Development Corporation, Revenue         
    Refunding Bonds (Army Retirement Residence Project), 6.30%, 7/01/12 (a)    1,500    1,708,545 
    Brazos River Authority, Texas, PCR, Refunding (TXU Energy Company Project),         
    AMT, Series C, 5.75%, 5/01/36        7,000    6,508,250 
    Dallas-Fort Worth, Texas, International Airport Facility Improvement         
    Corporation, Revenue Bonds (Learjet Inc.), AMT, Series A-1, 6.15%, 1/01/16    4,000    3,761,120 
    Dallas-Fort Worth, Texas, International Airport Facility Improvement         
    Corporation, Revenue Refunding Bonds, AMT, Series A-2, 9%, 5/01/29    3,000    2,250,600 
    Dallas-Fort Worth, Texas, International Airport, Joint Revenue Refunding         
    Bonds, AMT, Sub-Series A-2, 6.10%, 11/01/24 (b)        1,500    1,508,070 
    Gulf Coast, Texas, IDA, Solid Waste Disposal Revenue Bonds (Citgo Petroleum         
    Corporation Project), AMT, 7.50%, 5/01/25        2,440    2,536,892 
    Gulf Coast Waste Disposal Authority, Texas, Revenue Refunding Bonds         
    (International Paper Company), AMT, Series A, 6.10%, 8/01/24    2,000    1,864,980 
    Houston, Texas, Airport System Revenue Refunding Bonds, Sub-Lien, AMT,         
    Series A, 5.50%, 7/01/23 (e)        5,790    5,794,053 
    Houston, Texas, Health Facilities Development Corporation, Retirement         
    Facility Revenue Bonds (Buckingham Senior Living Community), Series A, 7%,         
    2/15/14 (a)        1,500    1,806,825 
    Lower Colorado River Authority, Texas, PCR (Samsung Austin Semiconductor),         
    AMT, 6.95%, 4/01/30        7,420    7,599,341 
    Sabine River Authority, Texas, PCR, Refunding (TXU Electric Company         
    Project/TXU Energy Company LLC), AMT, Series B, 5.75%, 5/01/30    5,000    4,609,600 
    Sheldon, Texas, Independent School District, GO, 5%, 2/15/33    1,460    1,465,971 
    Tarrant County, Texas, Health Facilities Development Corporation, Hospital         
    Revenue Refunding Bonds (Cumberland Rest, Inc. Project), VRDN, Series, 7%,         
    8/15/32 (d)(m)        690    690,000 
    Texas State Affordable Housing Corporation, S/F Mortgage Revenue Bonds         
    (Professional Educators Home Loan Program), AMT, Series A-3, 5.60%,         
    2/01/39 (f)(g)(h)        7,909    7,781,366 

8

BlackRock Muni Intermediate Duration Fund, Inc.             
Schedule of Investments August 31, 2008 (Unaudited)    (Percentages shown are based on Net Assets) 
 
            Par     
State    Municipal Bonds        (000)    Value 
 
 
 
 
    Texas State Affordable Housing Corporation, S/F Mortgage Revenue Bonds         
    (Professional Educators Home Loan Program), AMT, Series B, 5.95%,         
    12/01/39 (f)(g)(h)        $ 4,941    $ 4,930,525 
           
 
                72,460,350 
 
 
 
 
Virginia - 2.4%    James City County, Virginia, IDA, Residential Care Facility Revenue Refunding         
    Bonds, Series A, 5.75%, 3/01/17        3,285    3,293,377 
    James City County, Virginia, IDA, Residential Care Facility Revenue Refunding         
    Bonds, Series A, 6%, 3/01/23        1,150    1,126,045 
    Tobacco Settlement Financing Corporation of Virginia, Asset-Backed Revenue         
    Bonds, 5.625%, 6/01/15 (a)        7,800    8,756,670 
               
                13,176,092 
 
 
 
 
Washington -    Snohomish County, Washington, School District Number 015 (Edmonds), GO,         
2.0%    5%, 12/01/19 (i)        10,000    10,586,700 
 
 
 
 
Guam - 0.9%    Commonwealth of the Northern Mariana Islands, Guam, GO, Series A, 6.75%,         
    10/01/13 (a)        4,000    4,621,200 
    Commonwealth of the Northern Mariana Islands, Guam, GO, Series A, 6.75%,         
    10/01/33        250    252,330 
               
                4,873,530 
 
 
 
 
Puerto Rico -    Puerto Rico Commonwealth Aqueduct and Sewer Authority, Senior Lien         
12.8%    Revenue Bonds, Series A, 5%, 7/01/25 (n)        3,215    3,259,721 
    Puerto Rico Commonwealth Highway and Transportation Authority,         
    Subordinate Transportation Revenue Bonds, 5.75%, 7/01/21 (i)    4,375    4,505,638 
    Puerto Rico Electric Power Authority, Power Revenue Bonds, Series NN, 5.50%,         
    7/01/13 (a)        17,935    20,094,195 
    Puerto Rico Electric Power Authority, Power Revenue Bonds, Series WW,         
    5.50%, 7/01/38        6,350    6,470,269 
    Puerto Rico Housing Financing Authority, Capital Funding Program,         
    Subordinate Revenue Refunding Bonds, 5.125%, 12/01/27        13,900    13,689,971 
    Puerto Rico Industrial, Medical and Environmental Pollution Control Facilities         
    Financing Authority, Special Facilities Revenue Bonds (American Airlines Inc.),         
    Series A, 6.45%, 12/01/25        5,390    3,073,162 
    Puerto Rico Public Buildings Authority, Government Facilities Revenue         
    Refunding Bonds, Series D, 5.25%, 7/01/27        5,170    5,139,032 
    Puerto Rico Public Buildings Authority, Government Facilities Revenue         
    Refunding Bonds, Series I, 5.50%, 7/01/14 (a)(o)        8,000    8,873,600 
    Puerto Rico Public Finance Corporation, Commonwealth Appropriation         
    Revenue Bonds, Series E, 5.50%, 2/01/12 (a)        3,535    3,823,916 
               
                68,929,504 
 
 
 
 
U.S. Virgin    Virgin Islands Government Refinery Facilities, Revenue Refunding Bonds         
Islands - 1.6%    (Hovensa Coker Project), AMT, 6.50%, 7/01/21        1,860    1,863,962 
    Virgin Islands Public Finance Authority, Refinery Facilities Revenue Bonds         
    (Hovensa Refinery), AMT, 6.125%, 7/01/22        6,750    6,574,500 
               
                8,438,462 
 
 
 
 
    Total Municipal Bonds - 144.0%            777,721,256 
 
 
 
 

9

BlackRock Muni Intermediate Duration Fund, Inc.             
Schedule of Investments August 31, 2008 (Unaudited)    (Percentages shown are based on Net Assets) 
 
    Municipal Bonds Transferred to        Par     
State    Tender Option Bond Trusts (p)        (000)    Value 
 
 
 
 
California - 5.2%    Peralta, California, Community College District, GO (Election of 2000), Series         
    D, 5%, 8/01/30 (e)        $ 10,140    $ 10,287,638 
    San Jose, California, GO (Libraries, Parks and Public Safety Projects), 5%,         
    9/01/30 (b)        3,101    3,132,656 
    Sequoia, California, Unified High School District, GO, Refunding, Series B,         
    5.50%, 7/01/35 (e)        9,028    9,478,703 
    Tamalpais, California, Union High School District, GO (Election of 2001), 5%,         
    8/01/28 (e)        4,875    4,955,535 
               
                27,854,532 
 
 
 
 
Illinois - 2.4%    McHenry County, Illinois, Conservation District, GO, 5.125%, 2/01/207 (e)    12,695    13,164,955 
 
 
 
Massachusetts -    Massachusetts State School Building Authority, Dedicated Sales Tax Revenue         
1.6%    Bonds, Series A, 5%, 8/15/30 (e)        8,337    8,489,350 
 
 
 
 
New York - 2.1%    New York City, New York, Sales Tax Asset Receivable Corporation Revenue         
    Bonds, Series A, 5.25%, 10/15/27 (c)        11,100    11,577,189 
 
 
 
 
Texas - 6.1%    Harris County, Texas, Toll Road Revenue Refunding Bonds, Senior Lien, Series         
    A, 5.25%, 8/15/35 (e)        31,240    33,084,097 
 
 
 
 
    Total Municipal Bonds Transferred to             
    Tender Option Bond Trusts - 17.4%            94,170,123 
 
 
 
 
    Total Long-Term Investments (Cost - $873,241,524) - 161.4%        871,891,379 
 
 
 
    Total Investments (Cost - $873,241,524*) - 161.4%            871,891,379 
    Other Assets Less Liabilities - 1.8%            9,893,885 
    Liability for Trust Certificates, Including Interest             
     Expense and Fees Payable - (10.0)%            (54,096,957) 
    Preferred Shares, at Redemption Value - (53.2)%            (287,475,021) 
               
    Net Assets Applicable to Common Shares - 100.0%            $ 540,213,286 
               

* The cost and unrealized appreciation (depreciation) of investments as of August 31, 2008, as computed for federal income tax purposes, were as follows:

Aggregate cost    $ 818,723,481 
   
Gross unrealized appreciation    $ 18,520,854 
Gross unrealized depreciation    (19,329,921) 
   
Net unrealized depreciation    $ (809,067) 
   

(a)      U.S. government securities, held in escrow, are used to pay interest on this security as well as to retire the bond in full at the date indicated, typically at a premium to par.
 
(b)      MBIA Insured.
 
(c)      AMBAC Insured.
 
(d)      Variable rate security. Rate shown is as of report date. Maturity shown is the final maturity date.
 
(e)      FSA Insured.
 
(f)      FHLMC Collateralized.
 
(g)      FNMA Collateralized.
 
(h)      GNMA Collateralized.
 
(i)      FGIC Insured.
 
(j)      FHA Insured.
 
(k)      XL Capital Insured.
 

10

BlackRock Muni Intermediate Duration Fund, Inc.

Schedule of Investments August 31, 2008 (Unaudited)

(l)      CIFG Insured.
 
(m)      Radian Insured.
 
(n)      Assured Guaranty Insured.
 
(o)      Commonwealth Guaranteed.
 
(p)      Security represents bonds transferred to a tender option bond trust in exchange for which the Fund acquired residual interest certificates. These securities serve as collateral in a financing transaction.
 

11

BlackRock Muni Intermediate Duration Fund, Inc.

Schedule of Investments August 31, 2008 (Unaudited)

The inputs or methodology used for valuing securities are not necessarily an indication of the risk associated with investing in those securities. For information about the Fund's policy regarding valuation of investments and other significant accounting policies, please refer to the Fund's most recent financial statements as contained in its annual report.

The following table summarizes the inputs used as of August 31, 2008 in determining the fair valuation of the Fund's investments:

Valuation    Investments in 
Inputs    Securities 
 
Level 1    - 
Level 2    $ 871,891,379 
Level 3    - 
 
Total    $ 871,891,379 
   

12

Item 2 – Controls and Procedures

2(a) – The registrant’s principal executive and principal financial officers or persons performing
similar functions have concluded that the registrant’s disclosure controls and procedures (as
defined in Rule 30a-3(c) under the Investment Company Act of 1940, as amended (the
“1940 Act”)) are effective as of a date within 90 days of the filing of this report based on the
evaluation of these controls and procedures required by Rule 30a-3(b) under the 1940 Act
and Rule 13a-15(b) under the Securities Exchange Act of 1934, as amended.

2(b) – There were no changes in the registrant’s internal control over financial reporting (as
defined in Rule 30a-3(d) under the 1940 Act) that occurred during the registrant’s last fiscal
quarter that have materially affected, or are reasonably likely to materially affect, the
registrant’s internal control over financial reporting.

Item 3 – Exhibits

Certifications – Attached hereto

Pursuant to the requirements of the Securities Exchange Act of 1934 and the Investment
Company Act of 1940, the registrant has duly caused this report to be signed on its behalf by
the undersigned, thereunto duly authorized.

BlackRock Muni Intermediate Duration Fund, Inc.

By: Donald C. Burke
Donald C. Burke
Chief Executive Officer of
BlackRock Muni Intermediate Duration Fund, Inc.

Date: October 20, 2008

Pursuant to the requirements of the Securities Exchange Act of 1934 and the Investment
Company Act of 1940, this report has been signed below by the following persons on behalf
of the registrant and in the capacities and on the dates indicated.

By: Donald C. Burke
Donald C. Burke
Chief Executive Officer (principal executive officer) of
BlackRock Muni Intermediate Duration Fund, Inc.

Date: October 20, 2008

By: Neal J. Andrews
Neal J. Andrews
Chief Financial Officer (principal financial officer) of
BlackRock Muni Intermediate Duration Fund, Inc.

Date: October 20, 2008