(Mark One)

[X] ANNUAL REPORT PURSUANT TO SECTION 13 OR 15 (d) OF THE SECURITIES
EXCHANGE ACT OF 1934

For the Fiscal Year Ended March 31, 2001 OR

[ ] TRANSITION REPORT PURSUANT TO SECTION 13 OR 15 (d) OF THE SECURITIES
EXCHANGE ACT OF 1934

For the transition period from      to      .

Commission File Number: 000-24193

ATLANTIC DATA SERVICES, INC.
(Exact Name of Registrant as Specified in its Charter)

MASSACHUSETTS (State or Other Jurisdiction of Incorporation or Organization)

04-2696393 (I.R.S. Employer Identification Number)

One Batterymarch Park, Quincy, Massachusetts 02169
(Address of Principal Executive Offices) (Zip Code)
(617) 770 — 3333

(Registrant’s Telephone Number, Including Area Code)

Securities Registered Pursuant to Section 12(b) of the Act: None.

Securities Registered Pursuant to Section 12(g) of the Act: Common Stock, $.01 par value

(Title of Class)

Indicate by checkmark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes [ X ] No [     ]

Indicate by checkmark if disclosure of delinquent filers pursuant to Item 405 of Regulation S-K is not contained herein, and will not be contained, to the best of the registrant’s knowledge, in definitive proxy or information statements incorporated by reference in Part III of this Form 10-K or any amendment to this Form 10-K. [ X ]

The aggregate market value of the voting stock held by non-affiliates of the Company was approximately $10,542,158 on June 1, 2001 based on the last reported sale price of the Company’s Common Stock on the Nasdaq National Market on June 1, 2001 of $2.4000 per share. There were 13,023,126 shares of Common Stock issued and outstanding as of June 1, 2001

DOCUMENTS INCORPORATED BY REFERENCE — The Registrant intends to file a definitive proxy statement pursuant to Regulation 14A within 120 days of the end of the fiscal year ended March 31, 2001. Portions of such proxy statement are incorporated by reference into Part III of this report.