SC 13G: Schedule filed to report acquisition of beneficial ownership of 5% or more of a class of equity securities by passive investors and certain institutions

SCHEDULE 13G

Amendment No. 0
MFA Mortgage Investments Inc
Common Stock
Cusip #55272X102


Cusip #55272X102
Item 1: Reporting Person - FMR LLC
Item 4: Delaware
Item 5: 2,199,460
Item 6: 0
Item 7: 6,120,565
Item 8: 0
Item 9: 6,120,565
Item 11: 5.116%
Item 12: HC


Cusip #55272X102
Item 1: Reporting Person - Edward C. Johnson 3d
Item 4: United States of America
Item 5: 0
Item 6: 0
Item 7: 6,120,565
Item 8: 0
Item 9: 6,120,565
Item 11: 5.116%
Item 12: IN




SCHEDULE 13G - TO BE INCLUDED IN
STATEMENTS
FILED PURSUANT TO RULE 13d-1(b) or 13d-2(b)




Item 1(a). Name of Issuer:

MFA Mortgage Investments Inc

Item 1(b). Name of Issuer's Principal Executive Offices:

350 Park Avenue
21st Floor
New York, New York 10022


Item 2(a). Name of Person Filing:

FMR LLC

Item 2(b). Address or Principal Business Office or, if None,
Residence:

82 Devonshire Street, Boston,
Massachusetts 02109

Item 2(c). Citizenship:

Not applicable

Item 2(d). Title of Class of Securities:

Common Stock

Item 2(e). CUSIP Number:

55272X102

Item 3. This statement is filed pursuant to Rule 13d-1(b) or 13d-2(b)
and the person filing, FMR LLC, is a parent holding company
in accordance with Section 240.13d-1(b)(ii)(G). (Note: See
Item 7).

Item 4. Ownership

(a) Amount Beneficially Owned: 6,120,565

(b) Percent of Class: 5.116%

(c) Number of shares as to which such
person has:

(i) sole power to vote or to direct
the vote: 2,199,460

(ii) shared power to vote or to
direct the vote: 0

(iii) sole power to dispose or to
direct the disposition of: 6,120,565

(iv) shared power to dispose or to
direct the disposition of: 0



Item 5. Ownership of Five Percent or Less of a Class.

Not applicable.

Item 6. Ownership of More than Five Percent on Behalf of Another
Person.

Various persons have the right to receive or the power to
direct the receipt of dividends from, or the proceeds from the
sale of, the Common Stock of MFA Mortgage Investments
Inc. No one person's interest in the Common Stock of MFA
Mortgage Investments Inc is more than five percent of the
total outstanding Common Stock.

Item 7. Identification and Classification of the Subsidiary Which
Acquired the Security Being Reported on By the Parent
Holding Company.

See attached Exhibit A.

Item 8. Identification and Classification of Members of
the Group.

Not applicable. See attached Exhibit A.

Item 9. Notice of Dissolution of Group.

Not applicable.

Item 10. Certification.

By signing below I certify that, to the best of my knowledge
and belief, the securities referred to above were acquired in the
ordinary course of business and were not acquired for the
purpose of and do not have the effect of changing or
influencing the control of the issuer of such securities and
were not acquired in connection with or as a participant in any
transaction having such purpose or effect.

Signature

After reasonable inquiry and to the best of my knowledge and
belief, I certify that the information set forth in this statement
is true, complete and correct.

February 13, 2008
Date

/s/Eric D. Roiter
Signature

Eric D. Roiter
Duly authorized under Power of Attorney
dated December 30, 1997 by and on behalf of FMR Corp.
(now known as FMR LLC) and its direct and indirect
subsidiaries



SCHEDULE 13G - TO BE INCLUDED IN
STATEMENTS
FILED PURSUANT TO RULE 13d-1(b) or 13d-2(b)



Pursuant to the instructions in Item 7 of Schedule 13G,
Fidelity Management & Research Company ("Fidelity"), 82
Devonshire Street, Boston, Massachusetts 02109, a wholly-
owned subsidiary of FMR LLC and an investment adviser
registered under Section 203 of the Investment Advisers Act
of 1940, is the beneficial owner of 3,925,205 shares or 3.281%
of the Common Stock outstanding of MFA Mortgage
Investments Inc ("the Company") as a result of acting as
investment adviser to various investment companies registered
under Section 8 of the Investment Company Act of 1940.

Edward C. Johnson 3d and FMR LLC, through its
control of Fidelity, and the funds each has sole power to
dispose of the 3,925,205 shares owned by the Funds.

Members of the family of Edward C. Johnson 3d,
Chairman of FMR LLC, are the predominant owners, directly
or through trusts, of Series B voting common shares of FMR
LLC, representing 49% of the voting power of FMR LLC.
The Johnson family group and all other Series B shareholders
have entered into a shareholders' voting agreement under
which all Series B voting common shares will be voted in
accordance with the majority vote of Series B voting common
shares. Accordingly, through their ownership of voting
common shares and the execution of the shareholders' voting
agreement, members of the Johnson family may be deemed,
under the Investment Company Act of 1940, to form a
controlling group with respect to FMR LLC.

Neither FMR LLC nor Edward C. Johnson 3d,
Chairman of FMR LLC, has the sole power to vote or direct
the voting of the shares owned directly by the Fidelity Funds,
which power resides with the Funds' Boards of Trustees.
Fidelity carries out the voting of the shares under written
guidelines established by the Funds' Boards of Trustees.

Pyramis Global Advisors, LLC ("PGALLC"), 53 State
Street, Boston, Massachusetts, 02109, an indirect wholly-
owned subsidiary of FMR LLC and an investment adviser
registered under Section 203 of the Investment Advisers Act
of 1940, is the beneficial owner of 359,100 shares or 0.300%
of the outstanding Common Stock of MFA Mortgage
Investments Inc as a result of its serving as investment adviser
to institutional accounts, non-U.S. mutual funds, or investment
companies registered under Section 8 of the Investment
Company Act of 1940 owning such shares.

Edward C. Johnson 3d and FMR LLC, through its
control of PGALLC, each has sole dispositive power over
359,100 shares and sole power to vote or to direct the voting
of 359,100 shares of Common Stock owned by the
institutional accounts or funds advised by PGALLC as
reported above.

Pyramis Global Advisors Trust Company ("PGATC"),
53 State Street, Boston, Massachusetts, 02109, an indirect
wholly-owned subsidiary of FMR LLC and a bank as defined
in Section 3(a)(6) of the Securities Exchange Act of 1934, is
the beneficial owner of 1,818,864 shares or 1.520% of the
outstanding Common Stock of the MFA Mortgage
Investments Inc as a result of its serving as investment
manager of institutional accounts owning such shares.

Edward C. Johnson 3d and FMR LLC, through its
control of Pyramis Global Advisors Trust Company, each has
sole dispositive power over 1,818,864 shares and sole power
to vote or to direct the voting of 1,818,864 shares of Common
Stock owned by the institutional accounts managed by
PGATC as reported above.

Fidelity International Limited ("FIL"), Pembroke Hall,
42 Crow Lane, Hamilton, Bermuda, and various foreign-based
subsidiaries provide investment advisory and management
services to a number of non-U.S. investment companies and
certain institutional investors. FIL, which is a qualified
institution under section 240.13d-1(b)(1) pursuant to an SEC
No-Action letter dated October 5, 2000, is the beneficial
owner of 17,396 shares or 0.015% of the Common Stock
outstanding of the Company.

Partnerships controlled predominantly by members of
the family of Edward C. Johnson 3d, Chairman of FMR LLC
and FIL, or trusts for their benefit, own shares of FIL voting
stock with the right to cast approximately 47% of the total
votes which may be cast by all holders of FIL voting stock.
FMR LLC and FIL are separate and independent corporate
entities, and their Boards of Directors are generally composed
of different individuals.

FMR LLC and FIL are of the view that they are not
acting as a "group" for purposes of Section 13(d) under the
Securities Exchange Act of 1934 (the "1934" Act) and that
they are not otherwise required to attribute to each other the
"beneficial ownership" of securities "beneficially owned" by
the other corporation within the meaning of Rule 13d-3
promulgated under the 1934 Act. Therefore, they are of the
view that the shares held by the other corporation need not be
aggregated for purposes of Section 13(d). However, FMR
LLC is making this filing on a voluntary basis as if all of the
shares are beneficially owned by FMR LLC and FIL on a joint
basis.



SCHEDULE 13G - TO BE INCLUDED IN
STATEMENTS
FILED PURSUANT TO RULE 13d-1(b) or 13d-2(b)
RULE 13d-1(f)(1) AGREEMENT

The undersigned persons, on February 13, 2008, agree
and consent to the joint filing on their behalf of this Schedule
13G in connection with their beneficial ownership of the
Common Stock of MFA Mortgage Investments Inc at
December 31, 2007.

FMR LLC

By /s/ Eric D. Roiter
Eric D. Roiter
Duly authorized under Power of Attorney dated
December 30, 1997, by and on behalf of FMR Corp. (now
known as FMR LLC) and its direct and indirect subsidiaries

Edward C. Johnson 3d

By /s/ Eric D. Roiter
Eric D. Roiter
Duly authorized under Power of Attorney dated
December 30, 1997, by and on behalf of Edward C. Johnson
3d

Fidelity Management & Research Company

By /s/ Eric D. Roiter
Eric D. Roiter
Senior V.P. and General Counsel