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 for the period ended
         October 31, 2014 (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: January 5, 2015


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

Date: January 5, 2015