1
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                    FORM 11-K

(Mark One)

[X]      ANNUAL REPORT PURSUANT TO SECTION 15 (d) OF THE SECURITES EXCHANGE ACT
         OF 1934.

                   For the fiscal year ended December 31, 2000

                                       OR

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

           For the transition period from ____________ to ____________

Commission file number 000-24931

         A.       Full title of the plan and the address of the plan, if
                  different from that of the issuer named below:

                      S1 Corporation 401 (k) Savings Plan.

         B.       Name of issuer of the securities held pursuant to the plan and
                  the address of its principal executive offices:

     S1 Corporation, 3390 Peachtree Road, NE, Suite 1700, Atlanta, GA 30326

   2


                        REPORT OF INDEPENDENT ACCOUNTANTS

To the Participants and Plan Administrator of the
S1 Corporation 401(k) Savings Plan

In our opinion, the accompanying statements of net assets available for benefits
and the related statement of changes in net assets available for benefits
present fairly, in all material respects, the net assets available for benefits
of the S1 Corporation 401(k) Savings Plan (the "Plan") at December 31, 2000 and
1999, and the changes in net assets available for benefits for the year ended
December 31, 2000 in conformity with accounting principles generally accepted in
the United States of America. These financial statements are the responsibility
of the Plan's management; our responsibility is to express an opinion on these
financial statements based on our audits. We conducted our audits of these
statements in accordance with auditing standards generally accepted in the
United States of America, which require that we plan and perform the audit to
obtain reasonable assurance about whether the financial statements are free of
material misstatement. An audit includes examining, on a test basis, evidence
supporting the amounts and disclosures in the financial statements, assessing
the accounting principles used and significant estimates made by management, and
evaluating the overall financial statement presentation. We believe that our
audits provide a reasonable basis for our opinion.

Our audits were conducted for the purpose of forming an opinion on the basic
financial statements taken as a whole. The supplemental schedules of assets held
for investment purposes and reportable transactions are presented for the
purpose of additional analysis and are not a required part of the basic
financial statements but are supplementary information required by the
Department of Labor's Rules and Regulations for Reporting and Disclosure under
the Employee Retirement Income Security Act of 1974. These supplemental
schedules are the responsibility of the Plan's management. The supplemental
schedules have been subjected to the auditing procedures applied in the audits
of the basic financial statements and, in our opinion, are fairly stated in all
material respects in relation to the basic financial statements taken as a
whole.


/s/ PricewaterhouseCoopers LLP

Atlanta, Georgia
June 8, 2001


   3
S1 CORPORATION
401(K) SAVINGS PLAN
STATEMENTS OF NET ASSETS AVAILABLE FOR BENEFITS



                                                            DECEMBER 31,
                                                        2000            1999
                                                               
ASSETS
   Investments                                       $21,455,293     $21,294,853
   Restricted S1 Corporation common stock                758,332              --
                                                     -----------     -----------
      Total investments                               22,213,625      21,294,853
                                                     -----------     -----------
   Receivables
    Participant contributions                            202,479          86,260
    Employer contributions                                92,512          23,288
                                                     -----------     -----------
      Total receivables                                  294,991         109,548
                                                     -----------     -----------
      Net assets available for benefits              $22,508,616     $21,404,401
                                                     ===========     ===========


   The accompanying notes are an integral part of these financial statements.


                                       2
   4
S1 CORPORATION
401(K) SAVINGS PLAN
STATEMENT OF CHANGES IN NET ASSETS AVAILABLE FOR BENEFITS



                                                            FOR THE YEAR
                                                               ENDED
                                                             DECEMBER 31,
                                                                 2000
                                                         
Additions to net assets attributed to
 Interest and dividends                                     $  1,623,083
                                                            ------------

 Contributions
  Participant                                                  6,412,819
  Employer                                                     2,878,174
  Rollovers from other plans                                   1,598,569
                                                            ------------
    Total contributions                                       10,889,562
                                                            ------------
    Total additions                                           12,512,645
                                                            ------------

 Deductions from net assets attributed to
  Net depreciation in fair value of investments              (22,301,520)
  Benefits paid to participants                               (3,440,309)
                                                            ------------
    Total deductions                                         (25,741,829)
                                                            ------------

    Net decrease in net assets available for benefits
     before transfers from merged plans                      (13,229,184)

    Transfers of net assets available for plan benefits
     from merged plans                                        14,333,399
                                                            ------------
    Net increase in net assets available for benefits          1,104,215

 Net assets available for benefits
  Beginning of period                                         21,404,401
                                                            ------------
  End of period                                             $ 22,508,616
                                                            ============



   The accompanying notes are an integral part of these financial statements.


                                       3



   5

S1 CORPORATION
401(K) SAVINGS PLAN
NOTES TO FINANCIAL STATEMENTS

1.       DESCRIPTION OF THE PLAN

         The following description of the S1 Corporation 401(k) Savings Plan
         (the "Plan") provides only general information. Participants should
         refer to the Plan agreement for a more complete description of the
         Plan's provisions.

         GENERAL

         The Plan, which commenced on July 1, 1996, is a defined contribution
         plan covering all eligible employees of S1 Corporation (the "Company").
         Employees are eligible to participate immediately upon hire. Enrollment
         in the Plan occurs as soon as administratively feasible. The Plan is
         subject to certain provisions of the Employee Retirement Income
         Security Act of 1974 (ERISA), as amended.

         AMENDMENTS

         The Company changed its name from Security First Technologies, Inc. to
         S1 Corporation in November 1999. During January 2000, the Plan was
         amended to change its name from the Security First Technologies, Inc.
         401(k) Savings Plan to the S1 Corporation 401(k) Savings Plan.

         Also in January 2000, the custodian and recordkeeper was changed from
         Principal Life Insurance Company ("Principal") to T. Rowe Price Trust
         Company ("T. Rowe Price"). All net assets previously held by Principal
         were transferred into T. Rowe Price funds in January 2000.

         CONTRIBUTIONS

         Participants may contribute from 1% to 15% of their pretax earnings, up
         to a maximum of $10,500 in 2000 and $10,000 in 1999. Rollover
         contributions from other qualified plans are permitted. Effective
         January 2000, the Company makes matching contributions of $1.00 for
         every dollar that participants elect to contribute, up to a defined
         limit. Employer contributions are limited to the first 4% of the
         employee's eligible compensation and are made in the form of S1
         Corporation common stock. Participants are restricted from transferring
         employer contributions until 12 calendar months following the date the
         contribution was made. During 1999, the Company made matching
         contributions of $.25 for every dollar that participants elected to
         contribute to investments other than the S1 Corporation Common Stock
         Fund and $1.00 for every dollar that participants elected to contribute
         to the S1 Corporation Common Stock Fund, up to a defined limit.
         Employer contributions were limited to the first 4% of the employee's
         eligible compensation.

         ROLLOVERS FROM OTHER PLANS

         Transfers of account balances from other qualified retirement plans by
         newly employed participants are presented as "rollovers from other
         plans" in the Statement of Changes in Net Assets Available for
         Benefits.

         PARTICIPANT ACCOUNTS

         All contributions made to the selected investment funds are participant
         directed with the exception of employer matching contributions made to
         S1 Corporation common stock. Each participant's account is credited
         with the participant's contribution and allocations of (a) the
         Company's contribution and (b) Plan earnings. Allocations are based on
         participant


                                        4
   6

S1 CORPORATION
401(K) SAVINGS PLAN
NOTES TO FINANCIAL STATEMENTS

         earnings or account balances, as defined. The benefit to which a
         participant is entitled is the benefit that can be provided from the
         participant's vested account.

         INVESTMENTS

         The Plan's assets are invested in mutual funds and S1 Corporation
         common stock. Participants may change their investment allocation, as
         well as elections on future investments, at any time. Investment
         transfers from the S1 Corporation Common Stock Fund are subject to
         certain restrictions, as defined in the Plan agreement. The Plan
         allocates earnings to participants based on the ratio of the
         participant's account balance in each investment fund to the total of
         all participants' account balances in each investment fund. Earnings
         allocations to participant accounts occur at various intervals
         throughout the year and depend on which funds the participant has
         invested. For a description of the Plan's investment options,
         participants should refer to the Plan document and each fund's most
         current prospectus.

         VESTING

         Participants vest immediately in their contributions plus earnings
         thereon. Retroactively effective January 1, 2000, Company contributions
         plus earnings thereon vest at a rate of 25% per year starting with the
         first year of participation. Participants become fully vested in
         Company contributions upon reaching normal retirement age, total and
         permanent disability, or death. Prior to January 1, 2000, employees
         vested in their Company contributions at a rate of 33-1/3% per year
         starting with the third year of participation.

         As discussed in Note 4, the net assets of the Edify Corporation
         employee retirement plan were merged into the Plan during January 2000.
         Employees of Edify Corporation hired prior to January 1, 2000, will
         follow the vesting schedule of the Edify Corporation 401(k) Profit
         Sharing Plan (the "Edify Plan") for all balances transferred, together
         with earnings thereon, from the Edify Plan. The Edify Plan vests
         ratably over three years beginning with the first year of
         participation.

         DISTRIBUTION OF BENEFITS

         Participants who separate from service for any reason other than
         retirement and whose value of all vested accounts is $5,000 or less may
         have the value of their vested contributions distributed to them in a
         lump sum or elect a rollover distribution. If the vested account
         balance is greater than $5,000, the participant may elect to receive a
         lump sum distribution, make a rollover distribution or delay receiving
         the distribution until normal retirement age. Distribution of benefits
         to retired participants can be made in either lump sum or periodic
         payments. If participants die before receiving distribution of their
         accounts, the full amount of their accounts will be paid to their
         designated beneficiaries.

         As discussed in Note 4, the net assets of the Edify Corporation
         employee retirement plan were merged into the Plan during January 2000.
         Former Edify Corporation employees who have account balances as of
         December 31, 1999, are subject to special provisions. If the
         participant was married on the date benefits are to begin, the
         participant will automatically receive a joint and survivor annuity,
         unless he elects otherwise. If the participant was single on the date
         elections are to begin, the participant will receive a single life
         annuity, unless he elects otherwise. Participants may make a written
         election to waive the annuity form of payment during the 90-day period
         before the annuity is to begin.


                                       5
   7

S1 CORPORATION
401(K) SAVINGS PLAN
NOTES TO FINANCIAL STATEMENTS

         PARTICIPANT LOANS

         Beginning in January 2000, participants are allowed to borrow from
         their vested account balances. Participants may borrow at a minimum
         $1,000 and at a maximum the lesser of (a) $50,000 reduced by the
         participants' highest outstanding Plan loan balances during the 12
         months preceding the date of the loan or (b) one-half the value of the
         participants' vested interests in their accounts. Interest on the loans
         is 1% over the prime rate on the first business day of the calendar
         quarter immediately preceding the date as of which the loan is issued.
         Participants may have only one loan outstanding at any time.

         FORFEITURES

         Participants forfeit the nonvested portion of the employer matching
         contributions upon the earlier of (a) the distribution of the vested
         portion of their accounts, or (b) when the participant incurs five
         consecutive years with a break in service. Forfeitures are used by the
         Company to pay administrative expenses. Forfeitures not used to pay
         expenses shall be applied to reduce the earliest employer contributions
         made after the forfeitures are determined. Forfeitures amounted to
         $147,000 and $166,000 in 2000 and 1999, respectively.

         ADMINISTRATIVE EXPENSES

         Administrative expenses in excess of forfeitures are paid by the
         Company.

2.       SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

         BASIS OF PRESENTATION

         The accompanying financial statements have been prepared on the
         modified accrual basis.

         INVESTMENTS

         Investments are stated at fair value. Shares of registered investment
         companies are valued at quoted market prices, which represent the net
         asset value of shares held by the Plan at year-end. The Company's stock
         is valued at its quoted market price. Purchases and sales of
         investments are recorded on a trade-date basis.

         Net depreciation in fair value of investments, including realized gains
         and losses, represents the change in fair value during the year and
         realized gains and losses on investments sold or distributed during the
         year.

         CONTRIBUTIONS

         Employee and employer contributions are generally recorded in the
         period after the Company makes payroll deductions from the
         participants' earnings. At period end, receivables are recorded to
         reflect contributions made but not yet received.

         USE OF ESTIMATES

         The preparation of the financial statements in conformity with
         generally accepted accounting principles requires management to make
         estimates and assumptions that affect the reported amounts of assets,
         liabilities, and changes therein, and disclosures of contingent assets
         and liabilities. Actual results could differ from those estimates.


                                       6
   8

S1 CORPORATION
401(K) SAVINGS PLAN
NOTES TO FINANCIAL STATEMENTS

         PAYMENT OF BENEFITS

         Benefits are recorded when paid.

         RISKS AND UNCERTAINTIES

         The Plan's investments are subject to market risk due to changes in
         securities prices. In particular, the Plan's investments in S1
         Corporation common stock are exposed to significant market risk due to
         the high volatility of the Company's common stock price. At December
         31, 2000 and 1999, the Plan has a significant investment balance in S1
         Corporation common stock. Depending on the Company's common stock
         price, the Plan could experience significant fluctuations in asset
         values due to market volatility.

3.       INVESTMENTS

         The following table presents investments that represent 5 percent or
         more of the Plan's net assets:



                                                                              DECEMBER 31,
                                                                       2000                  1999
                                                                   ------------          ------------
                                                                                   
                  Janus Fund                                       $  1,272,478          $         --
                  T. Rowe Price Value Fund                            1,466,656                    --
                  T. Rowe Price Equity Index 500 Fund                 2,534,198                    --
                  T. Rowe Price Science & Technology Fund             2,876,563                    --
                  T. Rowe Price Mid-Cap Growth Fund                   1,978,682                    --
                  T. Rowe Price Small-Cap Stock Fund                  1,137,938                    --
                  T. Rowe Price Balanced Fund                         2,864,749                    --
                  T. Rowe Price Blue Chip Growth Fund                 2,645,091                    --
                  S1 Corporation Common Stock                         2,210,007            17,850,623


         The S1 Corporation Common Stock balance includes amounts contributed
         based on participant elections and employer matching contributions. As
         discussed in Note 1, employer matching contributions are restricted for
         a period of 12 calendar months from the date of contribution.

4.       PLAN MERGERS

         In November 1999, the Company completed the acquisitions of Edify
         Corporation ("Edify"), FICS Group, N.V. ("FICS") and VerticalOne
         Corporation ("VerticalOne"). In April 2000, the Company completed the
         acquisitions of Q-Up Systems, Inc. ("Q-Up") and Davidge Data Systems
         Corporation ("Davidge"). In November 2000, the Company completed the
         acquisition of LevelNext, Inc. ("LevelNext"). The employee retirement
         plans of Q-Up, Davidge and LevelNext were terminated and participants
         were given the option to enroll in the Plan upon acquisition. The
         assets of Edify's, FICS' (domestic operations only) and VerticalOne's
         employee retirement plans were merged into the Plan in January 2000. As
         a result of the Plan mergers, the number of participants increased from
         approximately 600 at December 31, 1999 to approximately 1,600 at
         December 31, 2000. The following table presents the value of plan net
         assets transferred into the Plan from the respective acquired company's
         plan:


                                       7
   9

S1 CORPORATION
401(K) SAVINGS PLAN
NOTES TO FINANCIAL STATEMENTS


                                          
                  Edify                      $12,313,768
                  FICS                         1,801,214
                  VerticalOne                    218,417


         Generally, the participants in these plans are given full credit for
         their service with their previous employers for purposes of both
         eligibility and vesting in the Plan.

5.       PLAN TERMINATION

         Although it has not expressed any intent to do so, the Company has the
         right under the Plan to discontinue its contributions at any time and
         to terminate the Plan subject to the provisions of ERISA. In the event
         of plan termination, participants will become 100 percent vested in
         their accounts.

6.       TAX STATUS

         The Internal Revenue Service has determined and informed the Company by
         a letter dated August 2, 1999, that the Plan and related trust are
         designed in accordance with applicable sections of the Internal Revenue
         Code (IRC). Although the Plan has been amended since receiving the
         determination letter, the Plan administrator and the Plan's tax counsel
         believe that the Plan is designed and is currently being operated in
         compliance with the applicable requirements of the IRC.

7.       RELATED PARTY TRANSACTIONS

         At December 31, 2000 and 1999, the Plan holds 420,954 and 228,488
         shares of S1 Corporation common stock with a market value of $2,210,007
         and $17,850,623, respectively.

         In January 2000, the custodian and recordkeeper changed to T. Rowe
         Price. Certain Plan investments are shares of mutual funds managed by
         T. Rowe Price and therefore, these transactions qualify as
         party-in-interest transactions. During 1999, certain Plan investments
         were shares of mutual funds managed by Principal. Principal was the
         custodian and the recordkeeper of the Plan during 1999 and, therefore,
         these transactions qualify as party-in-interest transactions. Fees
         incurred for administrative expenses amounted to approximately $20,000
         and $62,000 for the years ended December 31, 2000 and 1999,
         respectively.

8.       SUBSEQUENT EVENT

         On January 18, 2001, the Company sold VerticalOne, a wholly-owned
         subsidiary of the Company, to Yodlee.com, Inc. As a result, all
         individuals who were employees of VerticalOne and were Plan
         participants were severed from Plan participation effective January 18,
         2001. The Plan net assets attributable to the employees of VerticalOne
         will be transferred out of the Plan in accordance with the terms of the
         sale agreement.


                                       8
   10
S1 CORPORATION
401(K) SAVINGS PLAN
SCHEDULE H, LINE 4I - SCHEDULE OF ASSETS HELD FOR INVESTMENT PURPOSES
DECEMBER 31, 2000



                                                DESCRIPTION OF                                   CURRENT
IDENTITY OF ISSUE                                 INVESTMENT         SHARES        COST           VALUE
- -----------------                             -------------------    -------    ----------     -----------
                                                                                   
Participant Loans - Interest rates of
  7.5% to 10.5%                                 Participant Loans        N/A    $        --    $   252,636
  Janus Fund                                       Mutual Fund        38,224      1,676,498      1,272,478
* T. Rowe Price Value Fund                         Mutual Fund        76,588      1,344,663      1,466,656
* T. Rowe Price International Stock Fund           Mutual Fund        56,642      1,014,875        822,440
* T. Rowe Price International Discovery Fund       Mutual Fund        38,216      1,397,945        972,609
* T. Rowe Price Prime Reserve Fund                 Mutual Fund       766,782        766,781        766,781
* T. Rowe Price Equity Index 500 Fund              Mutual Fund        71,386      2,773,786      2,534,198
* T. Rowe Price Science & Technology Fund          Mutual Fund        80,870      4,782,294      2,876,563
* T. Rowe Price Mid-Cap Growth Fund                Mutual Fund        49,728      2,038,844      1,978,682
* T. Rowe Price Small-Cap Stock Fund               Mutual Fund        47,672      1,111,974      1,137,938
* T. Rowe Price Balanced Fund                      Mutual Fund       149,439      2,926,251      2,864,749
* T. Rowe Price GNMA Fund                          Mutual Fund        44,197        395,693        412,797
* T. Rowe Price Blue Chip Growth Fund              Mutual Fund        78,142      2,840,477      2,645,091
* S1 Corporation Common Stock                     Common Stock       276,510      3,824,105      1,451,675
* Restricted S1 Corporation Common Stock          Common Stock       144,444      2,631,882        758,332
                                                                                -----------    -----------
                                                                                $29,526,068    $22,213,625
                                                                                ===========    ===========


* Party-in-interest to the Plan


                                       9
   11
S1 CORPORATION
401(K) SAVINGS PLAN
SCHEDULE H, LINE 4J - SCHEDULE OF REPORTABLE TRANSACTIONS
FOR THE YEAR ENDED DECEMBER 31, 2000



                                               DESCRIPTION    PURCHASE       SELLING      COST OF     CURRENT OF VALUE    NET GAIN
IDENTITY OF ISSUE                               OF ASSET       PRICE          PRICE        ASSET           OF ASSET       OR (LOSS)
- -----------------                              -----------   ----------    ----------    ----------   ----------------    ---------
                                                                                                        
  Janus Fund                                   Mutual Fund   $2,993,896    $       --    $2,993,896      $2,993,896       $      --
  Janus Fund                                   Mutual Fund           --     1,302,177     1,315,918       1,302,177         (13,741)
* T. Rowe Price Value Fund                     Mutual Fund    1,781,970            --     1,781,970       1,781,970              --
* T. Rowe Price Value Fund                     Mutual Fund           --       439,518       434,887         439,518           4,631
* T. Rowe Price International Stock            Mutual Fund    1,288,987            --     1,288,987       1,288,987              --
* T. Rowe Price International Stock            Mutual Fund           --       257,726       271,994         257,726         (14,268)
* T. Rowe Price International Discovery Fund   Mutual Fund    1,625,173            --     1,625,173       1,625,173              --
* T. Rowe Price International Discovery Fund   Mutual Fund           --       191,628       226,586         191,628         (34,958)
* T. Rowe Price Prime Reserve Fund             Mutual Fund    1,609,991            --     1,609,991       1,609,991              --
* T. Rowe Price Prime Reserve Fund             Mutual Fund           --       828,072       828,072         828,072              --
* T. Rowe Price Equity Index 500 Fund          Mutual Fund    3,701,401            --     3,701,401       3,701,401              --
* T. Rowe Price Equity Index 500 Fund          Mutual Fund           --       894,291       923,302         894,291         (29,011)
* T. Rowe Price Science & Technology Fund      Mutual Fund    5,574,058            --     5,574,058       5,574,058              --
* T. Rowe Price Science & Technology Fund      Mutual Fund           --       691,563       789,253         691,563         (97,690)
* T. Rowe Price Mid-Cap Growth Fund            Mutual Fund    2,338,403            --     2,338,403       2,338,403              --
* T. Rowe Price Mid-Cap Growth Fund            Mutual Fund           --       310,276       300,623         310,276           9,653
* T. Rowe Price Small-Cap Stock                Mutual Fund    1,379,735            --     1,379,735       1,379,735              --
* T. Rowe Price Small-Cap Stock                Mutual Fund           --       287,880       270,273         287,880          17,607
* T. Rowe Price Balanced Fund                  Mutual Fund    3,811,112            --     3,811,112       3,811,112              --
* T. Rowe Price Balanced Fund                  Mutual Fund           --       886,551       885,186         886,551           1,365
* T. Rowe Price GNMA Fund                      Mutual Fund      661,141            --       661,141         661,141              --
* T. Rowe Price GNMA Fund                      Mutual Fund           --       269,598       265,487         269,598           4,111
* T. Rowe Price Blue Chip Growth Fund          Mutual Fund    3,652,606            --     3,652,606       3,652,606              --
* T. Rowe Price Blue Chip Growth Fund          Mutual Fund           --       841,141       817,449         841,141          23,692
* S1 Corporation Common Stock                 Common Stock    4,876,850            --     4,876,850       4,876,850              --
* S1 Corporation Common Stock                 Common Stock           --     1,364,294       940,368       1,364,294         423,926
* Restricted S1 Corporation Common Stock      Common Stock    2,795,097            --     2,795,097       2,795,097              --
* Restricted S1 Corporation Common Stock      Common Stock           --        46,424       152,541          46,424        (106,117)


  * Party-in-interest to the Plan



                                       10



   12

                                   SIGNATURES

The Plan. Pursuant to the requirements of the Securities Exchange Act of 1934,
the trustees (or other persons who administer the employee benefit plan) have
duly caused this annual report to be signed on its behalf by the undersigned
hereunto duly authorized.



                                       S1 Corporation 401 (k) Savings Plan

                                       401 (k) Plan Committee



Date: June 29, 2001                    By: /s/ Robert F. Stockwell
                                           ------------------------------------
                                           Name:  Robert F. Stockwell

                                           Title: Committee Member


                                       11


   13

                                  EXHIBIT INDEX



Exhibit No.                Exhibit
- -----------                -------
                        
    23                     Consent of Independent Accountants