Exhibit 5.1


                         Automatic Data Processing, Inc.
                             Corporate Headquarters
                                One ADP Boulevard
                         Roseland, New Jersey 07068-0456


                                                                  April 15, 1998


Board of Directors
Automatic Data Processing, Inc.
One ADP Boulevard
Roseland, NJ  07068

                       Re: Automatic Data Processing, Inc.
                           Registration Statement on Form S-8
                           ----------------------------------

Gentlemen:

        I have acted as counsel to Automatic Data Processing, Inc., a Delaware
corporation (the "Company"), in connection with the registration by the Company
of 5,954 shares of the Company's Common Stock, par value $.10 per share (the
"Shares"), pursuant to the Company's Registration Statement on Form S-8 which is
to be filed with the Securities and Exchange Commission on April 15, 1998 (the
"Registration Statement").

        In this connection, I have examined originals or copies, certified or
otherwise identified to my satisfaction, of such corporate records, certificates
and written and oral statements of officers and accountants of the Company and
of public officials, and other documents that I have considered necessary and
appropriate for this opinion and, based thereon, I advise you that, in my
opinion:

        1. The Company has been duly incorporated and is validly existing under
        the laws of the State of Delaware.

        2. The Company has corporate authority to issue the Shares in the
        manner and under the terms set forth in the Registration Statement.

        3. The Shares have been duly authorized and, when issued in accordance
        with the Time Resource Management, Inc. 1996 Incentive Stock Option
        Plan referred to in the Registration Statement, will be validly issued,
        fully paid and nonassessable.

        I hereby consent to the filing of this opinion as Exhibit 5.1
to the Registration Statement, to its use as part of the Registration Statement,
and to the use of my name in the Registration Statement.


                                                       Very truly yours,


                                                       /s/ James B. Benson
                                                       -------------------
                                                       James B. Benson
                                                       General Counsel