Exhibit 99.906CERT

        CERTIFICATION PURSUANT TO 18 U.S.C. 1350, AS ADOPTED PURSUANT TO
                 SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002
                 ---------------------------------------------

In connection with the Report of Mutual of America Investment Corporation (the
"Investment Corp.") on Form N-CSR for the annual period ended December 31, 2004
as filed with the Securities and Exchange Commission on the date hereof (the
"Report"), I, Manfred Altstadt, Chairman of the Board, President and Chief
Executive Officer of the Investment Corp., certify that:

      1.    The Report fully complies with the requirements of Section 13(a) or
            15(d) of the Securities Exchange Act of 1934; and

      2.    The information contained in the Report fairly presents, in all
            material respects, the financial condition and results of operations
            of the Investment Corp. for the period ended December 31, 2004.

Dated: February 28, 2005

                                        /s/ MANFRED ALTSTADT
                                        ----------------------------------------
                                        Manfred Altstadt
                                        Chairman of the Board,
                                        President and Chief Executive Officer of
                                        Mutual of America Investment Corporation




        CERTIFICATION PURSUANT TO 18 U.S.C. 1350, AS ADOPTED PURSUANT TO
                 SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002
                 ---------------------------------------------

In connection with the Report of Mutual of America Investment Corporation (the
"Investment Corp.") on Form N-CSR for the annual period ended December 31, 2004
as filed with the Securities and Exchange Commission on the date hereof (the
"Report"), I, John R. Greed, Executive Vice President, Chief Financial Officer
and Treasurer of the Investment Corporation, certify that:

      1.    The Report fully complies with the requirements of Section 13(a) or
            15(d) of the Securities Exchange Act of 1934; and

      2.    The information contained in the Report fairly presents, in all
            material respects, the financial condition and results of operations
            of the Investment Corp. for the period ended December 31, 2004.

Dated: February 28, 2004

                                        /s/ JOHN R. GREED
                                        ----------------------------------------
                                        John R. Greed
                                        Executive Vice President,
                                        Chief Financial Officer and Treasurer of
                                        Mutual of America Investment Corporation