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, 2010 (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, 2011

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

Date: January 4, 2011