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UNITEDSTATES
SECURITIESANDEXCHANGECOMMISSION
Washington,D.C.20549

FORM N-Q

QUARTERLY SCHEDULE OF PORTFOLIO HOLDINGS OF REGISTERED
MANAGEMENT INVESTMENT COMPANY

Investment Company Act file number 811-07156

Name of Fund: BlackRock MuniYield Insured Investment Fund (MFT)

Fund Address: 100 Bellevue Parkway, Wilmington, DE 19809

Name and address of agent for service: Donald C. Burke, Chief Executive Officer, BlackRock
MuniYield Insured Investment Fund, 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: 07/31/2009

Date of reporting period: 04/30/2009

Item 1 – Schedule of Investments

BlackRock MuniYield Insured Investment Fund       
Schedule of Investments April 30, 2009 (Unaudited)  (Percentages shown are based on Net Assets) 
      Par   
State  Municipal Bonds    (000)  Value 
Florida - 95.4%  Boynton Beach, Florida, Utility System Revenue Refunding Bonds, 6.25%,     
  11/01/20 (a)(b)    $ 700  $862,190 
Broward County, Florida, Educational Facilities Authority Revenue Bonds
  (Nova Southeastern University), 5%, 4/01/31 (c)    1,720  1,713,120 
  Daytona Beach, Florida, Utility System Revenue Refunding Bonds,     
  Series B, 5%, 11/15/27 (b)(d)    1,000  860,910 
  Emerald Coast, Florida, Utilities Authority, System Revenue Bonds,     
  5.25%, 1/01/36 (b)(d)    1,000  959,760 
  Florida HFA, Housing Revenue Bonds (Brittany Rosemont Apartments),     
  AMT, Series C-1, 6.75%, 8/01/14 (e)    845  846,377 
  Florida Housing Finance Corporation, Homeowner Mortgage Revenue     
  Bonds, AMT, Series 11, 5.95%, 1/01/32 (f)    1,515  1,517,212 
  Florida Housing Finance Corporation, Homeowner Mortgage Revenue     
  Refunding Bonds, AMT, Series 4, 6.25%, 7/01/22 (f)  260  267,642 
  Florida State Board of Education, Lottery Revenue Bonds,     
  Series A, 6%, 7/01/10 (b)(g)    6,190  6,643,418 
Florida State Turnpike Authority, Turnpike Revenue Bonds (Department
  of Transportation), Series B, 5%, 7/01/30    1,860  1,819,471 
  Hillsborough County, Florida, Aviation Authority Revenue Bonds, AMT,     
  Series A, 5.50%, 10/01/38 (c)    2,505  2,345,882 
  Hillsborough County, Florida, Aviation Authority, Revenue Refunding     
  Bonds, AMT, Series C, 5.75%, 10/01/26 (c)    1,000  1,009,350 
  Hillsborough County, Florida, School Board, COP, 5%, 7/01/29 (d)  1,000  969,050 
Jacksonville, Florida, Economic Development Commission, Health Care
  Facilities Revenue Bonds (Mayo Clinic-Jacksonville), Series B,     
  5.50%, 11/15/36 (d)    750  750,930 
  Jacksonville, Florida, Economic Development Commission, IDR     
  (Metropolitan Parking Solutions Project), AMT, 5.50%, 10/01/30 (h)  1,140  862,319 
  Jacksonville, Florida, Guaranteed Entitlement Revenue Refunding and     
  Improvement Bonds, 5.25%, 10/01/32 (b)(d)    1,455  1,454,927 
Jacksonville, Florida, Health Facilities Authority, Hospital Revenue Bonds
  (Baptist Medical Center Project), 5%, 8/15/37 (f)    2,875  2,658,110 
  Jacksonville, Florida, Port Authority Revenue Bonds, AMT,     
  6%, 11/01/38 (c)    2,550  2,553,188 
  Jacksonville, Florida, Port Authority, Seaport Revenue Bonds, AMT,     
  5.625%, 11/01/26 (d)    1,225  1,175,645 
Lakeland, Florida, Electric and Water Revenue Refunding Bonds, Series
  A, 5%, 10/01/28 (d)    2,000  1,973,020 
Portfolio Abbreviations         

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

AMT  Alternative Minimum Tax (subject to)  HFA  Housing Finance Agency 
COP  Certificates of Participation  IDA  Industrial Development Authority 
EDA  Economic Development Authority  IDR  Industrial Development Revenue Bonds 
GO  General Obligation Bonds  S/F  Single-Family 
    VRDN  Variable Rate Demand Notes 
           1   

BlackRock MuniYield Insured Investment Fund       
Schedule of Investments April 30, 2009 (Unaudited)  (Percentages shown are based on Net Assets) 
      Par   
State  Municipal Bonds    (000)         Value 
  Lee County, Florida, Airport Revenue Bonds, AMT, Series A,     
  6%, 10/01/29 (f)    $ 1,000  $ 1,006,410 
  Lee County, Florida, Capital Revenue Bonds, 5.25%, 10/01/23 (e)  2,285  2,299,875 
  Miami Beach, Florida, Water and Sewer Revenue Bonds,     
  5.75%, 9/01/25 (e)    2,000  2,048,940 
Miami-Dade County, Florida, Aviation Revenue Bonds, AMT, Series A, 5%,
  10/01/33 (f)    6,300  5,570,964 
  Miami-Dade County, Florida, Aviation Revenue Bonds (Miami     
  International Airport), AMT, Series A, 6%, 10/01/24 (b)  2,750  2,770,900 
Miami-Dade County, Florida, Aviation Revenue Refunding Bonds (Miami
  International Airport), AMT, Series A, 5.25%, 10/01/41 (f)  1,200  1,074,660 
Miami-Dade County, Florida, Aviation Revenue Refunding Bonds (Miami
  International Airport), AMT, Series A, 5.50%, 10/01/41 (f)  2,400  2,234,784 
Miami-Dade County, Florida, Expressway Authority, Toll System Revenue
  Bonds, Series B, 5.25%, 7/01/27 (b)(d)    1,000  1,006,670 
Miami-Dade County, Florida, IDA, IDR (BAC Funding Corporation Project),
  Series A, 5.375%, 10/01/30 (e)    1,655  1,661,835 
  Miami-Dade County, Florida, Solid Waste System Revenue Bonds,     
  5.25%, 10/01/30 (d)    1,865  1,866,921 
  Miami-Dade County, Florida, Special Obligation Revenue Bonds, Sub-     
  Series A, 5.186%, 10/01/31 (d)(i)    4,375  827,925 
  Miami-Dade County, Florida, Special Obligation Revenue Bonds, Sub-     
  Series A, 5.204%, 10/01/33 (d)(i)    5,735  922,819 
  Orange County, Florida, Educational Facilities Authority, Educational     
  Facilities Revenue Refunding Bonds (Rollins College Project),     
  5.50%, 12/01/32 (e)    4,765  4,768,574 
  Orange County, Florida, Health Facilities Authority, Hospital Revenue     
  Bonds (Orlando Regional Healthcare), 6%, 12/01/12 (g)  1,835  2,129,903 
Orange County, Florida, Sales Tax Revenue Refunding Bonds, Series A,
  5.125%, 1/01/23 (b)(d)    1,000  1,011,750 
Orange County, Florida, Tourist Development, Tax Revenue Refunding
  Bonds, 5%, 10/01/29 (e)    2,190  2,143,287 
  Orlando-Orange County Expressway Authority, Florida, Expressway     
  Revenue Bonds, Series B, 5%, 7/01/35 (e)    6,815  6,536,198 
  Orlando, Florida, Senior Tourist Development Tax Revenue Bonds (6th     
  Cent Contract Payments), Series A, 5.25%, 11/01/38 (c)  2,000  2,015,000 
Osceola County, Florida, Tourist Development Tax Revenue Bonds, Series
  A, 5.50%, 10/01/27 (b)(d)    1,100  1,105,379 
Palm Beach County, Florida, Criminal Justice Facilities Revenue Bonds,
  7.20%, 6/01/15 (b)(d)    1,500  1,796,070 
  Palm Beach County, Florida, School Board, COP, Refunding, Series D,     
  5.25%, 8/01/21 (f)    2,000  2,071,100 
  Palm Beach County, Florida, School Board, COP, Series A,     
  6%, 8/01/10 (b)(g)    5,000  5,382,100 

2

BlackRock MuniYield Insured Investment Fund       
Schedule of Investments April 30, 2009 (Unaudited)  (Percentages shown are based on Net Assets) 
      Par   
State  Municipal Bonds    (000)         Value 
  Panama City, Florida, Water and Sewer Revenue Bonds, Series B,     
  5.25%, 10/01/22 (d)    $ 1,500  $ 1,519,680 
  Polk County, Florida, Utility System Revenue Bonds,     
  5.25%, 10/01/22 (b)(d)    1,000  1,010,940 
  Port St. Lucie, Florida, Utility Revenue Bonds, 5.25%, 9/01/24 (d)  1,055  1,081,533 
Saint Johns County, Florida, Ponte Vedra Utility System Revenue Bonds,
  5%, 10/01/31 (f)    2,425  2,345,557 
Saint Johns County, Florida, Ponte Vedra Utility System Revenue Bonds,
  5%, 10/01/35 (f)    1,000  957,560 
  Saint Lucie, Florida, West Services District, Utility Revenue Bonds,     
  5.25%, 10/01/34 (d)    1,000  963,290 
  Santa Rosa County, Florida, School Board, COP, Refunding, Series 2,     
  5.25%, 2/01/26 (b)(d)    2,000  2,016,800 
South Lake County, Florida, Hospital District Revenue Bonds (South Lake
  Hospital Inc.), 5.80%, 10/01/34    1,000  875,400 
Village Center Community Development District, Florida, Recreational
  Revenue Bonds, Series A, 5.375%, 11/01/34 (d)    1,640  1,376,075 
Village Center Community Development District, Florida, Recreational
  Revenue Bonds, Series A, 5.125%, 11/01/36 (d)    1,000  801,190 
Village Center Community Development District, Florida, Utility Revenue
  Bonds, 5.25%, 10/01/23 (d)    2,295  2,075,414 
Village Center Community Development District, Florida, Utility Revenue
  Bonds, 5.125%, 10/01/28 (d)    3,030  2,712,183 
  Volusia County, Florida, IDA, Student Housing Revenue Bonds (Stetson     
  University Project), Series A, 5%, 6/01/25 (j)    1,000  887,270 
  Volusia County, Florida, IDA, Student Housing Revenue Bonds (Stetson     
  University Project), Series A, 5%, 6/01/35 (j)    1,000  801,030 
        102,918,507 
Georgia - 0.9%  Fulton County, Georgia, Water and Sewer Revenue Bonds,     
  5.25%, 1/01/35 (b)(d)    1,000  1,006,090 
Illinois - 2.9%  Chicago, Illinois, Transit Authority, Capital Grant Receipts Revenue     
  Bonds (Federal Transit Administration Section 5309 Formula Funds),     
  Series A, 6%, 6/01/26 (c)    1,400  1,563,142 
  Illinois Municipal Electric Agency, Power Supply Revenue Bonds,     
  Series A, 5.25%, 2/01/28 (b)(d)    1,565  1,577,755 
        3,140,897 
Kentucky - 1.0%  Kentucky State Property and Buildings Commission, Revenue Refunding     
  Bonds (Project Number 93), 5.25%, 2/01/27 (c)    1,000  1,042,560 
Louisiana - 1.9%  Louisiana State Citizens Property Insurance Corporation, Assessment     
  Revenue Bonds, Series C-3, 6.125%, 6/01/25 (c)    1,405  1,454,667 
New Orleans, Louisiana, Aviation Board Revenue Refunding Bonds, Series
  A-1, 6%, 1/01/23 (c)    375  385,766 
New Orleans, Louisiana, Aviation Board Revenue Refunding Bonds, Series
  A-2, 6%, 1/01/23 (c)    160  164,594 
        2,005,027 

3

BlackRock MuniYield Insured Investment Fund       
Schedule of Investments April 30, 2009 (Unaudited)  (Percentages shown are based on Net Assets) 
      Par   
State  Municipal Bonds    (000)         Value 
Michigan - 10.4%  Detroit, Michigan, Sewage Disposal System, Second Lien Revenue Bonds,     
  Series A, 5.50%, 7/01/36 (b)(k)    $ 1,500  $ 1,525,800 
  Detroit, Michigan, Sewage Disposal System, Second Lien Revenue     
  Refunding Bonds, Series E, 5.75%, 7/01/31 (b)(k)    2,270  2,326,682 
  Detroit, Michigan, Water Supply System Revenue Bonds, Second Lien,     
  Series B, 6.25%, 7/01/36 (f)    1,800  1,878,264 
  Detroit, Michigan, Water Supply System Revenue Bonds, Second Lien,     
  Series B, 7%, 7/01/36 (f)    200  220,974 
  Detroit, Michigan, Water Supply System Revenue Bonds, Senior Lien,     
  Series B, 5.50%, 7/01/35 (k)    3,750  3,883,500 
  Royal Oak, Michigan, Hospital Finance Authority, Hospital Revenue     
  Refunding Bonds (William Beaumont Hospital), 8.25%, 9/01/39  1,265  1,407,641 
        11,242,861 
Minnesota - 3.0%  Minneapolis, Minnesota, Health Care System, Revenue Refunding Bonds     
  (Fairview Health Services), Series B, 6.50%, 11/15/38 (c)  3,000  3,252,780 
Nevada - 1.9%  Clark County, Nevada, Water Reclamation District, GO, Series B,     
  5.50%, 7/01/29    2,000  2,090,180 
New Jersey - 2.3%  New Jersey EDA, School Facilities Construction Revenue Bonds, Series Z,     
  6%, 12/15/34 (c)    1,000  1,103,000 
  New Jersey Health Care Facilities Financing Authority Revenue Bonds     
  (Virtua Health), 5.50%, 7/01/38 (c)    1,400  1,373,960 
        2,476,960 
New York - 7.0%  New York City, New York, City Municipal Water Finance Authority,     
  Second General Resolution, Water and Sewer System Revenue Bonds,     
  Series FF-2, 5.50%, 6/15/40    1,100  1,157,057 
New York City, New York, City Transitional Finance Authority, Building
  Aid Revenue Bonds, Series S-3, 5.25%, 1/15/39    1,000  979,290 
New York City, New York, City Transitional Finance Authority, Building
  Aid Revenue Bonds, Series S-4, 5.50%, 1/15/29 (c)  2,000  2,090,100 
New York State Dormitory Authority, State Personal Income Tax Revenue
  Bonds (Education), Series B, 5.25%, 3/15/38    3,250  3,332,908 
        7,559,355 
Texas - 12.4%  Dallas, Texas, Civic Center Revenue Refunding and Improvement Bonds,     
  5.25%, 8/15/38 (c)    850  853,281 
  Harris County, Texas, Health Facilities Development Corporation,     
  Hospital Revenue Refunding Bonds (Memorial Hermann Healthcare     
  System), Series B, 7.25%, 12/01/35    500  530,065 
Houston, Texas, Combined Utility System, First Lien Revenue Refunding
  Bonds, Series A, 6%, 11/15/35 (c)    2,700  2,873,745 
Houston, Texas, Combined Utility System, First Lien Revenue Refunding
  Bonds, Series A, 6%, 11/15/36 (c)    2,055  2,215,639 
North Texas Tollway Authority, System Revenue Refunding Bonds, First
  Tier, Series A, 5.75%, 1/01/40 (c)    1,500  1,560,045 

4

BlackRock MuniYield Insured Investment Fund       
Schedule of Investments April 30, 2009 (Unaudited)  (Percentages shown are based on Net Assets) 
      Par   
State  Municipal Bonds         (000)         Value 
North Texas Tollway Authority, System Revenue Refunding Bonds, First
  Tier, Series K-1, 5.75%, 1/01/38 (c)    $ 1,400  $ 1,463,238 
  San Antonio, Texas, Electric and Gas Revenue Refunding Bonds,     
  Series A, 5.25%, 2/01/31    2,600  2,679,846 
  Tarrant County, Texas, Cultural Education Facilities Financing     
  Corporation, Revenue Refunding Bonds (CHRISTUS Health), Series A,     
  6.50%, 7/01/37 (c)    1,100  1,178,133 
        13,353,992 
Virginia - 1.1%  Virginia State Public School Authority, Special Obligation School     
  Financing Bonds (Fluvanna County), 6.50%, 12/01/35  1,100  1,239,579 
  Total Municipal Bonds - 140.2%      151,328,788 
  Municipal Bonds Transferred to       
  Tender Option Bond Trusts (l)       
District of Columbia -  District of Columbia, Water and Sewer Authority, Public Utility Revenue     
0.8%  Refunding Bonds, Senior Lien, Series A, 6%, 10/01/35  750  809,388 
Florida - 16.3%  Jacksonville Electric Authority, Florida, Saint John's River Power Park     
  System Revenue Bonds, Issue Three, Series 2, 5%, 10/01/37  1,290  1,215,399 
  Jacksonville, Florida, Sales Tax Revenue Bonds, 5%, 10/01/27 (d)  1,320  1,324,092 
  Manatee County, Florida, HFA, Homeowner Revenue Bonds, AMT,     
  Series A, 5.90%, 9/01/40 (m)(n)(o)    1,011  1,014,076 
  Miami-Dade County, Florida, Health Facilities Authority, Hospital     
  Revenue Refunding Bonds (Miami Children's Hospital), Series A,     
  5.625%, 8/15/17 (e)    6,960  7,677,437 
  Lee County, Florida, HFA, S/F Mortgage Revenue Bonds (Multi-County     
  Program), AMT, Series A-2, 6%, 9/01/40 (m)(n)(o)    1,725  1,857,773 
  South Broward, Florida, Hospital District, Hospital Revenue Bonds,     
  5.625%, 5/01/32 (d)    4,000  4,546,320 
        17,635,097 
Nevada - 2.0%  Clark County, Nevada, Water Reclamation District, Limited Tax, GO,     
  6%, 7/01/38    2,010  2,148,610 
  Total Municipal Bonds Transferred to       
  Tender Option Bond Trusts - 19.1%      20,593,095 
  Total Long-Term Investments       
  (Cost - $173,406,114) - 159.3%      171,921,883 
  Short-Term Securities       
Pennsylvania - 1.7%  Philadelphia, Pennsylvania, GO, Refunding, Series B, VRDN,     
  3.50%, 5/07/09 (f)(p)    1,800  1,800,000 
      Shares   
Money Market Funds -  CMA Florida Municipal Money Fund, 0.07% (q)(r)    448,365  448,365 
7.2%  FFI Institutional Tax-Exempt Fund, 0.64% (q)(r)    7,300,000  7,300,000 
        7,748,365 
  Total Short-Term Securities       
  (Cost - $9,548,365) - 8.9%      9,548,365 

5

BlackRock MuniYield Insured Investment Fund     
Schedule of Investments April 30, 2009 (Unaudited)  (Percentages shown are based on Net Assets) 
 
                                                                     Municipal Bonds    Value 
                                                                     Total Investments (Cost - $182,954,479*) - 168.2%  $ 181,470,248 
                                                                     Liabilities in Excess of Other Assets - (1.4)%    (1,464,373) 
                                                                     Liability for Trust Certificates, Including Interest     
                                                                     Expense and Fees Payable - (9.1)%    (9,834,383) 
                                                                     Preferred Shares, at Redemption Value - (57.7)%    (62,257,543) 
                                                                     Net Assets Applicable to Common Shares - 100.0%  $ 107,913,949 

* The cost and unrealized appreciation (depreciation) of investments as of April 30, 2009,

as computed for federal income tax purposes, were as follows:

Aggregate cost  $  170,888,575 
Gross unrealized appreciation  $  5,888,927 
Gross unrealized depreciation    (5,128,009) 
Net unrealized appreciation  $  760,918 

(a) Security is collateralized by Municipal or US Treasury Obligations.
(b) FGIC Insured.

(c) Assured Guaranty Insured.

(d) NPFGC Insured.

(e) AMBAC Insured.

(f) FSA Insured.

(g) US 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.

(h) ACA Insured.

(i) Represents a zero-coupon bond. Rate shown reflects the current yield as of report date.

(j) CIFG Insured.

(k) BHAC Insured.

(l) Securities represent 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.

(m) FHLMC Collateralized.

(n) FNMA Collateralized.

(o) GNMA Collateralized.

(p) Rate shown is as of report date and maturity shown is the final maturity date or the date the principal owed can be
recovered through demand.

(q) Investments in companies considered to be an affiliate of the Fund, for purposes of Section 2(a)(3) of the Investment
Company Act of 1940, were as follows:

Affiliate  Net Activity    Income   
CMA Florida Municipal Money Fund  (11,963,679)  $    37,051 
FFI Institutional Tax-Exempt Fund  7,300,000  $    1,966 

(r) Represents the current yield as of report date.

6

BlackRock MuniYield Insured Investment Fund
Schedule of Investments April 30, 2009 (Unaudited)

• Effective August 1, 2008, the Fund adopted Financial Accounting Standards Board Statement of Financial
Accounting Standards No. 157, "Fair Value Measurements" ("FAS 157"). FAS 157 clarifies the definition of
fair value, establishes a framework for measuring fair values and requires additional disclosures about
the use of fair value measurements. Various inputs are used in determining the fair value of investments,
which are as follows:

• Level 1 - price quotations in active markets/exchanges for identical securities

• Level 2 - other observable inputs (including, but not limited to: quoted prices for similar assets or liabilities in
markets that are active, quoted prices for identical or similar assets in markets that are not active, inputs
other than quoted prices that are observable for the assets or liabilities (such as interest rates, yield curves,
volatilities, prepayment speeds, loss severities, credit risks and default rates) or other market-corroborated
inputs)

• Level 3 - unobservable inputs based on the best information available in the circumstance, to the extent
observable inputs are not available (including the Fund's own assumption used in determining the fair value of
investments)

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 semi-
annual report.

The following table summarizes the inputs used as of April 30, 2009 in determining the fair valuation of the Fund's
investments:

Valuation    Investments in 
Inputs    Securities 
    Assets 
Level 1  $  7,748,365 
Level 2    173,721,883 
Level 3    - 
Total  $  181,470,248 

7

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 13(a)-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 MuniYield Insured Investment Fund

By: /s/ Donald C. Burke
Donald C. Burke
Chief Executive Officer of
BlackRock MuniYield Insured Investment Fund

Date: June 19, 2009

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/ Donald C. Burke
Donald C. Burke
Chief Executive Officer (principal executive officer) of
BlackRock MuniYield Insured Investment Fund

Date: June 19, 2009

By: /s/ Neal J. Andrews
Neal J. Andrews
Chief Financial Officer (principal financial officer) of
BlackRock MuniYield Insured Investment Fund

Date: June 19, 2009