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, 2006
Date of reporting period:   November 30, 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
NOVEMBER 30, 2005 (Unaudited)

BlackRock Insured Municipal Income Trust (BYM)

      Principal            
        Amount       Option Call    
    Rating1   (000)   Description   Provisions2   Value  
          LONG-TERM INVESTMENTS—155.3%        
            California—37.2%        
            California St., GO,        
    AAA   $ 5,000       5.00%, 2/01/32, MBIA   08/13 @ 100   $   5,150,300  
    AAA   5,000       5.00%, 3/01/33   03/15 @ 100   5,133,650  
    A   14,000 3      Dept. of Wtr. Res., Pwr. Sply. Rev., Ser. A, 5.375%, 5/01/12   N/A   15,580,740  
            Golden St. Tobacco Sec. Corp.,        
    AAA   25,000       Ser. A, 5.00%, 6/01/35, FGIC   06/15 @ 100   25,540,000  
    BBB   6,500       Ser. A-1, 6.625%, 6/01/40   06/13 @ 100   7,179,055  
    BBB   14,500       Ser. A-1, 6.75%, 6/01/39   06/13 @ 100   16,175,330  
    AAA   12,100   Infastructure & Econ. Dev. Bay Area Toll Brdgs., Ser. A, 5.00%, 7/01/36, AMBAC   07/13 @ 100   12,492,040  
    AAA   17,500   Met. Wtr. Dist. So. California, Ser. B-1, 5.00%, 10/01/33, FGIC   10/13 @ 100   18,105,500  
    AAA   15,000   San Francisco City & Cnty. Pub. Utils. Comm., Wtr. Rev., Ser. A, 5.00%, 11/01/31, FSA   11/11 @ 100   15,408,000  
    AAA   53,000   San Joaquin Hills Transp. Corridor Agcy., Toll Rd. Rev., Ser. A, Zero Coupon, 1/15/31, MBIA   No Opt. Call   14,891,410  
    AAA   10,910   Univ. of California, Ser. O, 5.00%, 9/01/28, FGIC   09/10 @ 101   11,313,234  
                    146,969,259  
            District of Columbia—2.6%        
    BBB   9,500   Tobacco Settlement Fin. Corp., 6.75%, 5/15/40   05/11 @ 101   10,264,085  
            Florida—7.6%        
    AAA   25,520   Miami Dade Cnty. Spl. Oblig. Cap. Apprec. Sub. Proj., Ser. A, Zero Coupon, 10/01/38, MBIA   10/15 @ 30.363   4,525,462  
    AAA   24,700   Orlando & Orange Cnty. Expwy. Auth., Expwy. Rev., Ser. B, 5.00%, 7/01/35, AMBAC   07/13 @ 100   25,484,225  
                    30,009,687  
            Georgia—6.5%        
    AAA   2,500   Atlanta Arpt. Passenger Fac., Ser. J, 5.00%, 1/01/34, FSA   01/15 @ 100   2,573,400  
            Atlanta Wtr. & Wstwtr.,        
    AAA   2,000       5.00%, 11/01/34, FSA   11/14 @ 100   2,062,260  
    AAA   3,235       5.00%, 11/01/37, FSA   11/14 @ 100   3,321,407  
    AAA   9,555       Ser. A, 5.00%, 11/01/38, FGIC   05/09 @ 101   9,853,020  
    BB-   10,000   De Kalb Cnty. Dev. Auth., PCR, General Mtrs. Corp. Proj., 6.00%, 3/15/21   12/12 @ 101   8,017,100  
                    25,827,187  
            Illinois—15.1%        
    AAA   11,550 3 Chicago Spec. Transp., 5.25%, 1/01/27, AMBAC   N/A   12,248,313  
            Chicago, GO,        
    AAA   13,000       Ser. A, 5.00%, 1/01/34, FSA   01/14 @ 100   13,346,840  
    AAA   7,000       Ser. A, 5.00%, 1/01/34, MBIA   01/13 @ 100   7,167,160  
            Met. Pier & Exposition Auth., Ded. St. Tax Rev., McCormick Place Expansion Proj.,        
    AAA   18,835       Ser. A, 5.00%, 12/15/28, MBIA   06/12 @ 101   19,381,968  
    AAA   15,000       Ser. B, Zero Coupon, 6/15/28, MBIA   No Opt. Call   5,040,450  
    AAA   2,400 4 O’Hare Intl. Arpt., Ser. A, 5.00%, 1/01/30, MBIA   01/15 @ 100   2,465,088  
                    59,649,819  
            Massachusetts—8.1%        
            Tpke. Auth., Met. Hwy. Sys. Rev.,        
    AAA   2,195       Ser. A, 5.00%, 1/01/37, MBIA   01/07 @ 102   2,226,718  
    AAA   24,000       Ser. A, 5.00%, 1/01/39, AMBAC   01/09 @ 101   24,441,120  
    AAA   5,000   Wtr. Res. Auth., Ser. B, 5.00%, 8/01/35, MBIA   08/17 @ 100   5,206,100  
                    31,873,938  
            Minnesota—1.3%        
    AAA   5,000   St. Paul Met. Arpt. Comm., 5.00%, 1/01/35, AMBAC   01/15 @ 100   5,109,600  
            Nevada—7.2%        
    AAA   6,000   Reno Transp. Proj., 5.125%, 6/01/32, AMBAC   06/12 @ 100   6,198,720  
            Truckee Meadows Wtr. Auth.,   
    AAA   10,000       Ser. A, 5.00%, 7/01/25, FSA   07/11 @ 100   10,273,400  
    AAA   6,500       Ser. A, 5.125%, 7/01/30, FSA   07/11 @ 100   6,730,425  
    AAA   5,000       Ser. A, 5.25%, 7/01/34, FSA   07/11 @ 100   5,192,800  
                    28,395,345  

1

BlackRock Insured Municipal Income Trust (BYM) (continued)

      Principal            
        Amount       Option Call    
    Rating1   (000)   Description   Provisions2   Value  
          New York—8.5%        
            New York City Mun. Wtr. Fin. Auth., Wtr. & Swr. Sys. Rev.,        
    AAA   $10,650       Ser. B, 5.00%, 6/15/36, FSA   12/14 @ 100   $  10,969,607  
    AAA   7,305       Ser. C, 5.00%, 6/15/35, AMBAC   06/14 @ 100   7,514,288  
    AAA   10,000   New York City Trust Cultural Recs., American Museum of Natural History Proj.,        
                Ser. A, 5.00%, 7/01/44, MBIA   07/14 @ 100   10,251,900  
    AAA   4,660   Sales Tax Asset Receivable Corp., Ser. A, 5.00%, 10/15/29, AMBAC   10/14 @ 100   4,849,196  
                    33,584,991  
            Ohio—4.6%        
    AAA   12,280   Air Qual. Dev. Auth., 4.80%, 1/01/34, FGIC   07/15 @ 100   12,316,963  
    AAA   6,000   Wtr. Dev. Auth, Poll. Ctrl. Facs. Rev., Dayton Pwr. & Lt., Ser. A, 4.80%, 1/01/34, FGIC   07/15 @ 100   5,944,980  
                    18,261,943  
            Pennsylvania—2.7%        
    BBB+   5,000   Lebanon Cnty. Hlth. Facs. Auth., Good Samaritan Hosp. Proj., 6.00%, 11/15/35   11/12 @ 101   5,340,800  
    AAA   5,200   Philadelphia Gas Wks., Ser. 3, 5.125%, 8/01/31, FSA   08/11 @ 100   5,352,516  
                    10,693,316  
            Puerto Rico—7.0%        
    AAA   25,000   Puerto Rico Comwlth Hwy. & Transp. Auth., Ser. L, 5.25%, 7/01/41   No Opt. Call   27,549,500  
            South Carolina—9.3%        
    AAA   5,000   Pub. Svc. Auth., Ser. B, 5.50%, 1/01/36, FSA   01/12 @ 100   5,342,250  
            Transp. Infrastructure Bank,        
    AAA   12,750       Ser. A, 5.00%, 10/01/33, AMBAC   10/12 @ 100   13,112,610  
    AAA   5,000       Ser. A, 5.00%, 10/01/33, AMBAC   10/13 @ 100   5,153,000  
    AAA   12,660       Ser. B, 5.125%, 10/01/26, AMBAC   10/11 @ 100   13,258,565  
                    36,866,425  
            Tennessee—3.9%        
            Knox Cnty. Hlth. Edl. & Hsg. Facs. Brd., Hosp. Facs. Rev.,   
    AAA   11,705       Ser. A, Zero Coupon, 1/01/22, FSA   01/13 @ 59.566   4,849,616  
    AAA   9,260       Ser. A, Zero Coupon, 1/01/23, FSA   01/13 @ 56.016   3,600,473  
    AAA   8,500       Ser. A, Zero Coupon, 1/01/24, FSA   01/13 @ 52.749   3,103,690  
    AAA   6,850       Ser. A, Zero Coupon, 1/01/25, FSA   01/13 @ 49.712   2,355,509  
    AAA   5,000       Ser. A, Zero Coupon, 1/01/26, FSA   01/13 @ 46.781   1,613,500  
                    15,522,788  
            Texas—22.8%        
    BBB-   3,700   Comal Cnty. Hlth. Facs., Hlth. Care Sys., McKenna Mem. Proj., Ser. A, 6.25%, 2/01/32   02/13 @ 100   3,927,106  
    AAA   10,030   Coppell Indpt. Sch. Dist., GO, Zero Coupon, 8/15/30   No Opt. Call   2,905,992  
    AAA   2,350   Dallas Area Rapid Trans., 5.00%, 12/01/31, AMBAC   12/11 @ 100   2,399,937  
            Harris Cnty., GO,        
    AAA   7,485       Zero Coupon, 8/15/25, MBIA   No Opt. Call   2,907,249  
    AAA   10,915       Zero Coupon, 8/15/28, MBIA   No Opt. Call   3,558,617  
    AAA   5,510       Toll Rd. Rev., 5.00%, 8/15/30, FSA   08/12 @ 100   5,651,331  
            Harris Cnty. Sports Auth.,        
    AAA   26,890       Ser. A-3, Zero Coupon, 11/15/38, MBIA   11/24 @ 43.826   4,271,208  
    AAA   27,675       Ser. A-3, Zero Coupon, 11/15/39, MBIA   11/24 @ 41.258   4,138,243  
    AAA   5,785       Ser. H, Zero Coupon, 11/15/38, MBIA   11/31 @ 64.91   935,319  
    AAA   6,160       Ser. H, Zero Coupon, 11/15/39, MBIA   11/31 @ 60.976   935,581  
    AAA   9,500   Northside Indpt. Sch. Dist., Sch. Bldg. Rmkt., GO, 5.125%, 6/15/29   06/14 @ 100   9,930,255  
            San Antonio Wtr.,        
    AAA   9,350       5.125%, 5/15/29, FGIC   05/14 @ 100   9,756,538  
    AAA   10,000       5.125%, 5/15/34, FGIC   05/14 @ 100   10,399,200  
    AAA   25,000   Tpke. Auth., Central Sys. Rev., Ser. A, 5.00%, 8/15/42, AMBAC   08/12 @ 100   25,396,000  
    BBB+   3,000   Tyler Cnty. Hlth. Facs. Dev., Mother Frances Hosp., 6.00%, 7/01/31   07/12 @ 100   3,128,640  
                    90,241,216  
            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   3,284,310  
    A3   4,000       Ser. B, 5.875%, 6/01/17   11/10 @ 102   4,379,080  
                    7,663,390  

2

BlackRock Insured Municipal Income Trust (BYM) (continued)

      Principal            
        Amount       Option Call    
    Rating1   (000)   Description   Provisions2   Value  
          Washington—8.7%        
    AAA   $9,610       Central Washington Univ. Sys. Rev., 5.00%, 5/01/34, FGIC   05/14 @ 100   $  9,875,044  
    AAA   3,655   Chelan Cnty. Pub. Util. Dist. 1, Chelan Hydro Sys. Proj., Ser. C, 5.125%, 7/01/33, AMBAC   07/12 @ 100   3,773,093  
    AAA   4,500   Port of Seattle, Ser. A, 5.00%, 4/01/31, FGIC   10/11 @ 100   4,602,285  
    AAA   9,500   Seattle, GO, Ser. F, 5.125%, 12/15/28, MBIA   12/08 @ 100   9,766,380  
    AAA   6,380   Washington, GO, Ser. A, 5.00%, 7/01/25, FSA   07/11 @ 100   6,599,025  
                    34,615,827  
            West Virginia—0.3%        
    AAA   1,295   Econ. Dev. Auth., Correctional Juvenile Safety Proj., Ser. A, 5.00%, 6/01/29, MBIA   06/14 @ 100   1,340,260  
            Total Long-Term Investments (cost $593,101,976)       614,438,576  
        Shares         
        (000)           
            MONEY MARKET FUND—0.7%        
        2,650   AIM Tax Free Investment Co. Cash Reserve Portfolio (cost $2,650,000)   N/A   2,650,000  
            Total Investments—156.0% (cost $595,751,9765)       $ 617,088,576  
            Other assets in excess of liabilities—1.9%       7,488,414  
            Preferred shares at redemption value, including dividends payable—(57.9)%       (229,035,780)  
            Net Assets Applicable to Common Shareholders—100%       $ 395,541,210  

1   Using the higher of Standard & Poor’s, Moody’s Investors Service or Fitch Ratings 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 prerefunded. 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   Security, or a portion thereof, pledged as collateral with a value of $2,465,088 on 544 short U.S. Treasury Note futures contracts expiring December 2005, 400 short U.S. Treasury Note futures contracts expiring March 2006 and 342 short U.S. Treasury Bond futures contracts expiring March 2006. The value of such contracts on November 30, 2005 was $140,878,688, with an unrealized gain of $1,813,701.  
5   Cost for Federal tax purposes is $595,836,245. The net unrealized appreciation on a tax basis is $21,252,331, consisting of $25,344,836 gross unrealized appreciation and $4,092,505 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 80.2% of the Trust’s managed assets. The Trust had the following insurance concentrations:

AMBAC —
26.3%
FGIC —
21.2%
FSA —
15.4%
MBIA —
16.9%
Other —
0.4%

KEY TO ABBREVIATIONS

AMBAC — American Municipal Bond Assurance Corp.   GO — General Obligation
FGIC — Financial Guaranty Insurance Co.   MBIA — Municipal Bond Insurance Assoc.
FSA — Financial Security Assurance   PCR — Pollution Control Revenue
         

3

Item 2. Controls and Procedures.

(a) The Registrant's principal executive and principal financial officers have evaluated the Registrant's disclosure controls and procedures within 90 days of this filing and have concluded, as of that date, that the Registrant’s disclosure controls and procedures were reasonably designed to ensure that information required to be disclosed by the Registrant in this Form N-Q was recorded, processed, summarized, and reported within the required time periods and that information to be disclosed by the Registrant in this Form N-Q was accumulated and communicated to the Registrant’s management , including its principle executive and principle financial officers, as appropriate to allow timely decisions regarding required disclosure.

(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 (17 CFR 270.30a -3(d)) 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.

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 and Principal Financial Officer
Date: January 25, 2006

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: President and Principal Executive Officer
Date: January 25, 2006

By:     /s/ Henry Gabbay                                                                                                                   
Name: Henry Gabbay
Title: Treasurer and Principal Financial Officer
Date: January 25, 2006