As filed with the U.S. Securities and Exchange Commission on March 21, 2019

File No. 002-73948

File No. 811-03258

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM N-1A

REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933	☒
Pre-Effective Amendment No.__	☐
Post-Effective Amendment No. 233	☒
And/or
REGISTRATION STATEMENT UNDER THE INVESTMENT COMPANY ACT OF 1940	☐
Amendment No. 235	☒

(Check appropriate box or boxes.)

DFA INVESTMENT DIMENSIONS GROUP INC.

(Exact Name of Registrant as Specified in Charter)

6300 Bee Cave Road, Building One, Austin, TX 78746

(Address of Principal Executive Office)      (Zip Code)

Registrant’s Telephone Number, including Area Code (512) 306-7400

Catherine L. Newell, Esquire, President and General Counsel

DFA Investment Dimensions Group Inc.,

6300 Bee Cave Road, Building One, Austin, TX 78746

(Name and Address of Agent for Service)

Please send copies of all communications to:

Jana L. Cresswell, Esquire

Stradley, Ronon, Stevens & Young, LLP

2600 One Commerce Square

Philadelphia, PA 19103

(215) 564-8048

It is proposed that this filing will become effective (check appropriate box)

☒              immediately upon filing pursuant to paragraph (b)

☐              on (date) pursuant to paragraph (b)

☐              60 days after filing pursuant to paragraph (a)(1)

☐              on (date) pursuant to paragraph (a)(1)

☐              75 days after filing pursuant to paragraph (a)(2)

☐              on (date) pursuant to paragraph (a)(2) of rule 485.

If appropriate, check the following box:

☐ this post-effective amendment designates a new effective date for a previously filed post-effective amendment.

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933 and the Investment Company Act of 1940, as amended, the Registrant certifies that it meets all the requirements for effectiveness of this Registration Statement under Rule 485(b) under the Securities Act and has duly caused this Post-Effective Amendment Nos. 233/235 to its Registration Statement on Form N-1A to be signed on its behalf by the undersigned, hereunto duly authorized in the City of Austin, the State of Texas on this 21^ST day of March, 2019.

DFA INVESTMENT DIMENSIONS GROUP INC.

(Registrant)

By:  /s/ Catherine L. Newell*        

       Catherine L. Newell, President

       (Signature and Title)

Pursuant to the requirements of the Securities Act of 1933, Post-Effective Amendment Nos. 233/235 to this Registration Statement has been signed below by the following persons in the capacities and on the date indicated:

NAME	TITLE	DATE
/s/ David G. Booth*	Director and	March 21, 2019
David G. Booth	Chairman
/s/ Gerard K. O’Reilly*	Co-Chief Executive Officer	March 21, 2019
Gerard K. O’Reilly	and Chief Investment Officer
/s/ David P. Butler*	Co-Chief Executive Officer	March 21, 2019
David P. Butler
/s/Gregory K. Hinkle*	Chief Financial Officer,	March 21, 2019
Gregory K. Hinkle	Treasurer and Vice President
/s/ George M. Constantinides*	Director	March 21, 2019
George M. Constantinides
/s/ Douglas W. Diamond*	Director	March 21, 2019
Douglas W. Diamond
/s/ Roger G. Ibbotson*	Director	March 21, 2019
Roger G. Ibbotson
/s/ Edward P. Lazear*	Director	March 21, 2019
Edward P. Lazear
/s/ Myron S. Scholes*	Director	March 21, 2019
Myron S. Scholes
/s/ Abbie J. Smith*	Director	March 21, 2019
Abbie J. Smith

*By:	/s/ Valerie A. Brown
	Valerie A. Brown
	Attorney-In-Fact (Pursuant to a Power of Attorney)

EXHIBIT INDEX
Index No.	Description of Exhibit
EX-101.INS	XBRL Instance Document
EX-101.SCH	XBRL Taxonomy Extension Schema Document
EX-101.CAL	XBRL Taxonomy Extension Calculation Linkbase
EX-101.DEF	XBRL Taxonomy Extension Definition Linkbase
EX-101.LAB	XBRL Taxonomy Extension Labels Linkbase
EX-101.PRE	XBRL Taxonomy Extension Presentation Linkbase