CERTIFICATIONS PURSUANT TO SECTION 906 OF THE
                          SARBANES-OXLEY ACT OF 2002

David G. Booth, Principal Executive Officer, and David R. Martin, Principal
Financial Officer, of DFA Investment Dimensions Group Inc., a Maryland
corporation (the "Registrant"), each certify that:

    1. The Registrant's periodic report on Form N-CSR/A for the period ended
       October 31, 2011 (the "Report") fully complies with the requirements of
       Section 13(a) or Section 15(d) of the Securities Exchange Act of 1934,
       as amended, as applicable; and

    2. The information contained in the Report fairly presents, in all material
       respects, the financial condition and results of operations of the
       Registrant.


By:  /s/ David G. Booth
     ------------------------------------
     David G. Booth
     Principal Executive Officer
     DFA Investment Dimensions Group Inc.

Date: March 16, 2012


By:  /s/ David R. Martin
     ------------------------------------
     David R. Martin
     Principal Financial Officer
     DFA Investment Dimensions Group Inc.

Date: March 16, 2012