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:__811-21178______

_______BlackRock Insured Municipal Income Trust_______
(Exact name of registrant as specified in charter)

100 Bellevue Parkway, Wilmington, DE    19809 
(Address of principal executive offices) 
 
(Zip code) 

Robert S. Kapito, President

BlackRock Insured Municipal Income Trust

_______40 East 52nd Street, New York, NY 10022_______
(Name and address of agent for service)

Registrant's telephone number, including area code:_888-825-2257__________________

Date of fiscal year end:___August 31, 2005

Date of reporting period:__May 31, 2005_________________________________

Item 1. Schedule of Investments.

The registrant’s unaudited schedule of investments as of the close of the reporting period pursuant to Rule 30b1-5 under the Investment Company Act of 1940 is as follows:


PORTFOLIO OF INVESTMENTS
MAY 31, 2005 (Unaudited)
BlackRock Insured Municipal Income Trust (BYM)

  Principal          
    Amount     Option Call    
Rating1   (000)   Description Provisions2   Value  
      LONG-TERM INVESTMENTS—149.5%      
        California—37.5%      
        California St.,      
AAA   $ 5,000         5.00%, 2/01/32, MBIA 08/13 @ 100   $  5,266,600  
AAA   5,000         5.00%, 3/01/33 03/15 @ 100   5,284,050  
A   14,000   Dept. of Wtr. Res., Pwr. Sply. Rev., Ser. A, 5.375%, 5/01/22 05/12 @ 101   15,222,900  
        Golden St. Tobacco Sec. Corp.,  
BBB   6,500         Ser. A-1, 6.625%, 6/01/40 06/13 @ 100   6,981,520  
BBB   14,500         Ser. A-1, 6.75%, 6/01/39 06/13 @ 100   15,788,325  
AAA   22,500         Ser. B, 5.00%, 6/01/43, FSA 06/13 @ 100   23,312,475  
AAA   12,100   Infrastructure & Econ. Dev., Bay Area Toll Brdgs., Ser. A, 5.00%, 7/01/36, AMBAC 07/13 @ 100   12,773,849  
AAA   17,500   Met. Wtr. Dist. So. California, Ser. B-1, 5.00%, 10/01/33, FGIC 10/13 @ 100   18,499,425  
AAA   5,000   Sacramento Cnty. San. Dist. Fin. Auth., Sacramento Regl. Cnty. San., Ser. A,      
              5.00%, 12/01/35, AMBAC 12/14 @ 100   5,318,600  
AAA   15,000   San Francisco City & Cnty. Pub. Utils. Comm., Wtr. Rev., Ser. A,
      5.00%, 11/01/31, FSA		 11/11 @ 100   15,659,250  
AAA   53,000   San Joaquin Hills Transp. Corridor Agcy., Toll Road Rev., Ser. A, Zero Coupon,      
              1/15/31, MBIA No Opt. Call   14,735,060  
AAA   10,910   Univ. of California, Ser. O, 5.00%, 9/01/28, FGIC 09/10 @ 101   11,451,354  
              150,293,408  
        District of Columbia—2.5%      
BBB   9,500   Tobacco Settlement Fin. Corp., 6.75%, 5/15/40 05/11 @ 101   10,202,240  
        Florida—6.5%      
AAA   24,700   Orlando & Orange Cnty. Expwy. Auth., Florida Expwy. Rev., Ser. B,
      5.00%, 7/01/35, AMBAC		 07/13 @ 100   25,989,093  
        Georgia—8.2%      
        Atlanta Arpt. Passenger Fac., FSA,      
AAA   4,950         Ser. C, 5.00%, 1/01/33 07/14 @ 100   5,177,651  
AAA   2,500         Ser. J, 5.00%, 1/01/34 01/15 @ 100   2,614,125  
        Atlanta Wtr. & Wstwtr.,      
AAA   2,000         5.00%, 11/01/34, FSA 11/14 @ 100   2,118,460  
AAA   3,235         5.00%, 11/01/37, FSA 11/14 @ 100   3,418,910  
AAA   9,555         Ser. A, 5.00%, 11/01/38, FGIC 05/09 @ 101   9,866,970  
Baa3   10,000   De Kalb Cnty. Dev. Auth., PCR, General Mtrs. Corp. Proj., 6.00%, 3/15/21 12/12 @ 101   9,662,800  
              32,858,916  
        Illinois—15.2%      
        Chicago, GO,      
AAA   13,000         Ser. A, 5.00%, 1/01/34, FSA 01/14 @ 100   13,608,660  
AAA   7,000         Ser. A, 5.00%, 1/01/34, MBIA 01/13 @ 100   7,295,400  
AAA   11,550 3 Chicago Spec. Transp., 5.25%, 1/01/31, AMBAC N/A   12,403,198  
        Met. Pier & Exposition Auth., Ded. St. Tax Rev., McCormick Place
      Expansion Proj., MBIA,		      
AAA   18,835         Ser. A, 5.00%, 12/15/28 06/12 @ 101   19,761,494  
AAA   15,000         Ser. B, Zero Coupon, 6/15/28 No Opt. Call   5,133,300  
AAA   2,400 4 O'Hare Intl. Arpt., Ser. A, 5.00%, 1/01/30, MBIA 01/15 @ 100   2,515,296  
              60,717,348  
        Massachusetts—8.1%      
        Tpke. Auth., Met. Hwy. Sys. Rev.,      
AAA   2,195         Ser. A, 5.00%, 1/01/37, MBIA 01/07 @ 102   2,269,652  
AAA   24,000         Ser. A, 5.00%, 1/01/39, AMBAC 01/09 @ 101   24,761,040  
AAA   5,000   Wtr. Res. Auth., Ser. B, 5.00%, 8/01/35, MBIA 08/17 @ 100   5,338,250  
              32,368,942  
        Michigan—1.3%      
AAA   5,000   Detroit City Sch. Dist., GO, Ser. A, 5.125%, 5/01/31, FSA 05/12 @ 100   5,271,700  
        Nevada—7.2%      
AAA   6,000   Reno Transp. Proj., 5.125%, 6/01/32, AMBAC 06/12 @ 100   6,318,480  
        Truckee Meadows Wtr. Auth., Ser. A, FSA,      
AAA   10,000         5.00%, 7/01/25 07/11 @ 100   10,474,000  
AAA   6,500         5.125%, 7/01/30 07/11 @ 100   6,847,880  
AAA   5,000         5.25%, 7/01/34 07/11 @ 100   5,295,350  
              28,935,710  

1
BlackRock Insured Municipal Income Trust (BYM) (continued)

  Principal          
    Amount     Option Call    
Rating1   (000)   Description Provisions2   Value  
      New Jersey—1.3%      
AAA   $ 4,935   Newark Hsg. Auth., Port Auth. Port Newark Marine Term. Rental Backed,
      Redev. Projs.,		      
              5.00%, 1/01/37, MBIA 01/14 @ 100   $ 5,180,467  
        New York—9.1%      
        New York City Mun. Wtr. Fin. Auth., Wtr. & Swr. Sys. Rev.,      
AAA   12,650         Ser. B, 5.00%, 6/15/36, FSA 12/14 @ 100   13,397,362  
AAA   7,305         Ser. C, 5.00%, 6/15/35, AMBAC 06/14 @ 100   7,729,201  
AAA   10,000   New York City Trust Cultural Resources, American Museum of Natural History,      
              Ser. A, 5.00%, 7/01/44, MBIA 07/14 @ 100   10,528,900  
AAA   4,660   Sales Tax Asset Receivable Corp., Ser. A, 5.00%, 10/15/29, AMBAC 10/14 @ 100   4,998,270  
              36,653,733  
        Pennsylvania—5.3%      
AAA   5,420   Iroquois Sch. Dist., 5.00%, 2/01/45, FSA 08/15 @ 100   5,670,241  
BBB+   5,000   Lebanon Cnty. Hlth. Facs. Auth., Good Samaritan Hosp. Proj., 6.00%, 11/15/35 11/12 @ 101   5,323,300  
AAA   5,200   Philadelphia Gas Wks., Ser. 3, 5.125%, 8/01/31, FSA 08/11 @ 100   5,449,808  
AAA   4,560   Tpke. Comm., 5.00%, 7/15/41, AMBAC 07/11 @ 101   4,762,510  
              21,205,859  
      South Carolina—9.4%      
AAA   5,000   So. Carolina Pub. Svc. Auth., Ser. B, 5.50%, 1/01/36, FSA 01/12 @ 100   5,450,950  
        So. Carolina Transp. Infrastructure Bank, AMBAC,      
AAA   12,750         Ser. A, 5.00%, 10/01/33 10/12 @ 100   13,403,310  
AAA   5,000         Ser. A, 5.00%, 10/01/33 10/13 @ 100   5,285,550  
AAA   12,660         Ser. B, 5.125%, 10/01/26 10/11 @ 100   13,470,367  
              37,610,177  
        Tennessee—3.9%      
        Knox Cnty. Hlth. Edl. & Hsg. Facs. Brd., Hosp. Facs. Rev., Ser. A, FSA,      
AAA   11,705         Zero Coupon, 1/01/22 01/13 @ 59.566   4,834,867  
AAA   9,260         Zero Coupon, 1/01/23 01/13 @ 56.016   3,594,362  
AAA   8,500         Zero Coupon, 1/01/24 01/13 @ 52.749   3,097,740  
AAA   6,850         Zero Coupon, 1/01/25 01/13 @ 49.712   2,350,851  
AAA   5,000         Zero Coupon, 1/01/26 01/13 @ 46.781   1,608,850  
              15,486,670  
        Texas—23.0%      
BBB   3,700   Comal Cnty. Hlth. Facs., Hlth. Care Sys., McKenna Mem. Proj., Ser. A,
      6.25%, 2/01/32		 02/13 @ 100   3,991,079  
AAA   10,030   Coppell Indpt. Sch. Dist., Zero Coupon, 8/15/30 No Opt. Call   2,910,907  
AAA   2,350   Dallas Area Rapid Trans., 5.00%, 12/01/31, AMBAC 12/11 @ 100   2,443,695  
        Harris Cnty.,      
AAA   7,485         GO, Zero Coupon, 8/15/25, MBIA No Opt. Call   2,905,452  
AAA   10,915         GO, Zero Coupon, 8/15/28, MBIA No Opt. Call   3,582,631  
AAA   5,510         Toll Road Rev., 5.00%, 8/15/30, FSA 08/12 @ 100   5,749,795  
        Harris Cnty. Sports Auth., MBIA,      
AAA   26,890         Ser. A-3, Zero Coupon, 11/15/38 11/24 @ 43.826   4,425,287  
AAA   27,675         Ser. A-3, Zero Coupon, 11/15/39 11/24 @ 41.258   4,287,411  
AAA   5,785         Ser. H, Zero Coupon, 11/15/38 11/31 @ 64.91   991,144  
AAA   6,160         Ser. H, Zero Coupon, 11/15/39 11/31 @ 60.976   991,391  
AAA   9,500   Northside Indpt. Sch. Dist., Sch. Bldg. Rmkt, 5.125%, 6/15/29 06/14 @ 100   10,118,070  
        San Antonio Wtr., FGIC,      
AAA   9,350         5.125%, 5/15/29 05/14 @ 100   9,989,446  
AAA   10,000         5.125%, 5/15/34 05/14 @ 100   10,645,500  
AAA   25,000   Texas Tpke. Auth., Central Sys. Rev., Ser. A, 5.00%, 8/15/42, AMBAC 08/12 @ 100   25,884,250  
BBB+   3,000   Tyler Cnty. Hlth. Facs. Dev., Mother Frances Hosp., 6.00%, 7/01/31 07/12 @ 100   3,175,020  
              92,091,078  
        Virginia—1.9%      
        Chesterfield Cnty. Indl. Dev. Auth., PCR, Elec. & Pwr. Co.,      
A3   3,000         Ser. A, 5.875%, 6/01/17 11/10 @ 102   3,348,540  
A3   4,000         Ser. B, 5.875%, 6/01/17 11/10 @ 102   4,464,720  
              7,813,260  

2
BlackRock Insured Municipal Income Trust (BYM) (continued)

  Principal          
    Amount     Option Call    
Rating1   (000)   Description Provisions2   Value  
      Washington—8.8%      
AAA   $ 9,610   Central Washington Univ. Sys. Rev., 5.00%, 5/01/34, FGIC 05/14 @ 100   $  10,110,489  
AAA   3,655   Chelan Cnty. Pub. Util. Dist. 1, Chelan Hydro Sys., Ser. C,
      5.125%, 7/01/33, AMBAC		 07/12 @ 100   3,848,605  
AAA   4,500   Port of Seattle, Ser. A, 5.00%, 4/01/31, FGIC 10/11 @ 100   4,652,460  
AAA   9,500   Seattle, GO, Ser. F, 5.125%, 12/15/28, MBIA 12/08 @ 100   9,957,235  
AAA   6,380   Washington, GO, Ser. A, 5.00%, 7/01/25, FSA 07/11 @ 100   6,710,484  
              35,279,273  
        West Virginia—0.3%      
AAA   1,295   Econ. Dev. Auth., Correctional Juvenile Safety, Ser. A, 5.00%, 6/01/29, MBIA 06/14 @ 100   1,371,936  
        Total Long-Term Investments (cost $563,084,217)     599,329,810  
        SHORT-TERM INVESTMENTS—6.1%      
        Alaska—1.80%      
A1+   7,300 5 Valdez Alaska Marine Term., Refdg. Exxon Pipeline Co. Proj., Ser. A,
      2.87%, 6/01/05, FRDD		 N/A   7,300,000  
        Maryland—1.5%      
A1+   6,045 5 Hlth. & Higher Edl. Facs. Auth., Pooled Ln. Prog. Proj., Ser. D, 2.95%, 6/02/05, FRWD N/A   6,045,000  
        Ohio—0.3%      
VMIG1   1,000 5 Hamilton Cnty. Hosp. Facs., 3.01%, 6/02/05, FRWD N/A   1,000,000  
        Pennsylvania—0.2%      
VMIG1   700 5 Higher Ed. Facs. Auth., St. Sys. Higher Ed., Ser. A, 2.93%, 6/02/05, MBIA, FRWD N/A   700,000  
        Wyoming—1.2%      
A1+   4,850 5 Lincoln Cnty. PCR, Exxon Proj., Ser. D, 2.81%, 6/01/05, FRDD N/A   4,850,000  
        Puerto Rico—1.1%      
A-1   1,800 5 Gov’t. Dev. Bank, 2.85%, 6/01/05, MBIA, FRWD N/A   1,800,000  
A-1+   2,500 5 Hwy. & Transp. Auth., Transp. Rev., Ser. A, 2.90%, 6/01/05, AMBAC, FRWD N/A   2,500,000  
              4,300,000  
   
           
    Shares          
    (000)          
   
           
        Money Market Fund—0.0%      
    50   AIM Tax Free Investment Co. Cash Reserve Portfolio N/A   50,000  
        Total Short-Term Investments (cost $24,245,000)     24,245,000  
        Total Investments—155.6% (cost $587,329,6176)     $ 623,574,810  
        Other assets in excess of liabilities—1.5%     6,211,048  
        Preferred shares at redemption value, including dividends payable—(57.1)%     (229,007,359 )
        Net Assets Applicable to Common Shareholders—100%     $ 400,778,499  

1 Using the higher of S&P’s, Moody’s or Fitch’s rating.
2 Date (month/year) and price of the earliest optional call or redemption. There may be other call provisions at varying prices at later dates.
3 This bond is prefunded. U.S. government securities, held in escrow, are used to pay interest on this security, as well as retire the bond in full at the date indicated, typically at a premium to par.
4 Securities, or a portion thereof, pledged as collateral with a value of $2,515,296 on 1,683 short U.S. Treasury Note futures contracts expiring Sept. 2005. The value of such contracts on May 31, 2005 was $190,626,047, with an unrealized loss of $2,736,310.
5 For purposes of amortized cost valuation, the maturity date of this instrument is considered to be the earlier of the next date on which the security can be redeemed at par, or the next date on which the rate of interest is adjusted.
6 Cost for Federal income purposes is $587,441,737. The net unrealized appreciation on a tax basis is $36,133,073 consisting of $36,470,273 gross unrealized appreciation and $337,200 gross unrealized depreciation.

The value (market value plus accrued interest) of securities that are covered by insurance, which ensures the payment of principal and interest, represent approximately 81.3% of the Trust’s managed assets. 

KEY TO ABBREVIATIONS
 
AMBAC — American Municipal Bond Assurance Corporation FSA — Financial Security Assurance
FGIC — Financial Guaranty Insurance Company GO — General Obligation
FRDD — Floating Rate Daily Demand MBIA — Municipal Bond Insurance Association
FRWD — Floating Rate Weekly Demand PCR — Pollution Control Revenue

3

Item 2. Controls and Procedures.

(a) The registrant's principal executive officer and principal financial officer have evaluated the registrant's disclosure controls and procedures within 90 days of this filing and have concluded that the registrant’s disclosure controls and procedures are effective, as of that date, in ensuring that information required to be disclosed by the registrant in this Form N-Q was recorded, processed, summarized, and reported timely.

(b) The registrant's principal executive officer and principal financial officer are aware of no changes in the registrant's internal control over financial reporting that occurred during the registrant's most recent fiscal quarter that has materially affected, or is reasonably likely to materially affect, the registrant's internal control over financial reporting.

Item 3. Exhibits.

Separate certifications of the registrant’s principal executive and financial officers pursuant to Section 302 of the Sarbanes-Oxley Act of 2002 are attached as EX-99.CERT.

SIGNATURES

      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.

(Registrant)___BlackRock Insured Municipal Income Trust___

By: __/s/ Henry Gabbay_____________________________________________
Name: Henry Gabbay
Title: Treasurer
Date: July 22, 2005

      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: __/s/ Robert S. Kapito_____________________________________________
Name: Robert S. Kapito
Title: Principal Executive Officer
Date: July 22, 2005

By: __/s/ Henry Gabbay_____________________________________________
Name: Henry Gabbay
Title: Principal Financial Officer
Date: July 22, 2005