DFA INVESTMENT DIMENSIONS GROUP INC.

                   Multiple Class Plan Pursuant to Rule 18f-3


                                 I. INTRODUCTION

This  Multiple  Class Plan (the  "Plan")  has been  adopted by a majority of the
Board of Directors of DFA  Investment  Dimensions  Group Inc.  (the  "Company"),
including a majority of the Directors who are not "interested  persons" (as that
term is defined in the  Investment  Company Act of 1940,  as amended  (the "1940
Act")) of the Company (together, the "Independent Directors"),  pursuant to Rule
18f-3 under the 1940 Act,  with respect to each series of the Company  listed on
Schedule A attached hereto (each a "Fund," and together, the "Funds").

The Plan  designates two classes of shares of each Fund and, in accordance  with
Rule 18f-3 under the 1940 Act,  sets forth the  differences  between the classes
with  respect  to  distribution  arrangements,   shareholder  services,  expense
allocations and any related conversion features or exchange privileges.

The  Company's  Board of  Directors,  including  a majority  of the  Independent
Directors,  has determined that the Plan,  including the allocation of expenses,
is in the best interests of the Company as a whole,  each Fund and each class of
shares offered by a Fund.

                            II. ELEMENTS OF THE PLAN

Class  Designation:  Each Fund's  shares  shall be divided into  Investor  Class
Shares and Class R Shares.  Subject to  ratification  by the Board of Directors,
the Company may change the names designating the Funds' classes of shares.

Differences  in  Availability:  Investor  Class  Shares  shall be  available  to
eligible investors,  as disclosed in the Funds'  prospectuses,  and will be sold
subject to the supervision of DFA Securities Inc. ("DFAS"). Class R Shares shall
be  available to those  investors  who desire an expanded  array of  shareholder
services,  as disclosed in the Funds' prospectuses,  and will be sold subject to
the supervision of DFAS.

Differences in Distribution Arrangements:  None.

Differences in Shareholder  Services:  Other than shareholder services that will
be  provided  pursuant  to a  Shareholder  Services  Agreement  approved  by the
Company's  Board of Directors for the Class R Shares of each Fund,  the services
offered to shareholders of all classes of the Funds shall be the same.

Expense  Allocation:  All expenses of each Fund shall be allocated  between each
class of shares in  accordance  with Rule 18f-3 under the 1940 Act,  except that
the fees and expenses incurred by a Fund under a Shareholder  Services Agreement
for its  Class R  Shares  shall  be  allocated  to the  Class R  Shares  and the
following  types of expenses  specific to each class shall be  allocated to such
class:

     o    transfer agency and other recordkeeping costs;

     o    Securities  and  Exchange  Commission  and  blue sky  registration  or
          qualification fees;

     o    printing and postage  expenses  related to printing  and  distributing
          materials,  such as shareholder  reports,  prospectuses and proxies to
          current   shareholders   of  a  particular   class  or  to  regulatory
          authorities with respect to such class;

     o    audit or accounting fees or expenses relating solely to such class;

     o    the expenses of  administrative  personnel and services as required to
          support the shareholders of such class;

     o    litigation or other legal expenses relating solely to such class;

     o    Directors'  fees and expenses  incurred as a result of issues relating
          solely to such class; and

     o    other expenses  subsequently  identified and determined to be properly
          allocated to such class.

Conversion  Features:  Investor  Class  Shares and Class R Shares  shall have no
conversion features.

Exchange  Privileges:  Investor Class Shares of each Fund shall be  exchangeable
only for Investor Class Shares of other Funds. Class R Shares of each Fund shall
be exchangeable  only for Class R Shares of other Funds.  Each exchange shall be
made based upon the relative net asset values of the classes as set forth in the
prospectuses of the Funds.

Voting and Other Rights:  All class shares shall each have: (a) exclusive voting
rights on any  matter  submitted  to  shareholders  that  relates  solely to its
arrangements; (b) separate voting rights on any matter submitted to shareholders
in which the  interests  of one class  differ  from the  interests  of the other
class;  and (c) in all other  respects,  the same rights and  obligations as the
other class.

Additional Information: The Plan is qualified by and subject to the terms of the
then current prospectuses for the applicable classes;  provided,  however,  that
none of the terms set forth in any such prospectuses  shall be inconsistent with
the terms of the classes  contained in the Plan. The  prospectuses for the Funds
contain  additional  information about the classes and the Funds' multiple class
structure.




Adopted:  April 1, 2004





                                   Schedule A
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                         U.S. Small Cap Value Portfolio