SEC Form 3

FORM 3

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person* MERRILL LYNCH & CO., INC. (Last) (First) (Middle) 4 WORLD FINANCIAL CENTER (Street) NEW YORK, NY 10080 (City) (State) (Zip)	2. Date of Event Requiring Statement (Month/Day/Year) 12/31/2008	3. Issuer Name and Ticker or Trading Symbol BLACKROCK MUNIHOLDINGS INSURED INVESTMENT FUND [ MFL ]
		4. Relationship of Reporting Person(s) to Issuer (Check all applicable) Director X 10% Owner Officer (give title below) Other (specify below)	5. If Amendment, Date of Original Filed (Month/Day/Year)
			6. Individual or Joint/Group Filing (Check Applicable Line) Form filed by One Reporting Person X Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Beneficially Owned
1. Title of Security (Instr. 4)	2. Amount of Securities Beneficially Owned (Instr. 4)	3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	4. Nature of Indirect Beneficial Ownership (Instr. 5)
Auction Rate Preferred(1)	2,420(1)(2)	I	See footnote(3)

Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 4)	2. Date Exercisable and Expiration Date (Month/Day/Year)		3. Title and Amount of Securities Underlying Derivative Security (Instr. 4)		4. Conversion or Exercise Price of Derivative Security	5. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

1. Name and Address of Reporting Person* MERRILL LYNCH & CO., INC. (Last) (First) (Middle) 4 WORLD FINANCIAL CENTER (Street) NEW YORK, NY 10080 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

1. Name and Address of Reporting Person* MERRILL LYNCH, PIERCE, FENNER & SMITH INC. (Last) (First) (Middle) 4 WORLD FINANCIAL CENTER (Street) NEW YORK, NY 10080 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

Explanation of Responses:

1. The securities reported on this Form 3 are subject to repurchase under the terms of Merrill Lynch & Co.'s ("MLCO") settlement with the Securities and Exchange Commission (the "Commission"), et alia, with respect to certain auction rate securities ("Subject Securities") sold by MLCO and/or held by customers in accounts at MLCO. The repurchases of the Subject Securities by MLCO, and the reporting of its holdings of such Subject Securities by MLCO, are being made in reliance on the Auction Rate Securities-Global Relief Letter issued by the Commission on September 22, 2008 (the "Relief Letter"). In reliance on the Relief Letter, we are reporting our holdings of each series of preferred stock of the issuer on a consolidated basis as a single class of securities.

2. In further reliance on the Relief Letter, we will not file Forms 4 to report changes in our beneficial ownership of the issuer's preferred stock. However, in compliance with the terms of the Relief Letter, we hereby undertake to provide upon request by the Commission, the issuer or a security holder of the issuer, complete information regarding the number of equity securities of the issuer purchased or sold at each different price and date of all transactions in such securities that occurred after we became a 10% owner but prior to the date of this filing.

3. Merrill Lynch & Co., Inc. indirectly through its wholly-owned subsidiary Merrill Lynch, Pierce, Fenner & Smith Incorporated owns 2,420 shares of the issuer's preferred stock.

	Merrill Lynch & Co, Inc., By: /s/ Pia Thompson, Assistant Secretary	01/09/2009
	Merrill Lynch, Pierce, Fenner & Smith, Inc., By: /s/ Pia Thompson, Assistant Secretary	01/09/2009
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 5 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
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