================================================================================

     As filed with the Securities and Exchange Commission on April 27, 2001

                                               Registration No. 333-____________

                UNITED STATES SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                    FORM S-8

             REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933
                                _________________

                      TRANSACTION SYSTEMS ARCHITECTS, INC.
             (Exact name of registrant as specified in its charter)

              Delaware                              47-0772104
    (State or other jurisdiction of      (I.R.S. Employer Identification No.)
     incorporation or organization)

                             224 South 108th Avenue
                              Omaha, Nebraska 68154
          (Address of principal executive offices, including zip code)
                                _________________

           Transaction Systems Architects, Inc. 1999 Stock Option Plan
     Transaction Systems Architects, Inc. 1999 Employee Stock Purchase Plan
                            (Full title of the plans)

                              David P. Stokes, Esq.
                          General Counsel and Secretary
                      Transaction Systems Architects, Inc.
                             224 South 108th Avenue
                              Omaha, Nebraska 68514
                                 (402) 334-5101
(Name, address and telephone number, including area code, of agent for service)
<TABLE>
<CAPTION>

                         CALCULATION OF REGISTRATION FEE

================================== =================== ===================== ====================== ================
                                                         Proposed Maximum      Proposed Maximum        Amount of
                                      Amount to be      Offering Price Per    Aggregate Offering     Registration
    Title of Securities to be        Registered (1)         Share (2)                Price                Fee
           Registered
================================== =================== ===================== ====================== ================
<S>                                 <C>                <C>                   <C>                    <C>
1999 STOCK OPTION PLAN              1,000,000 shares         $7.755               $ 7,755,000          $1,938.75
     Class A Common Stock,
     $0.005 par value
---------------------------------- ------------------- --------------------- ---------------------- ----------------

1999 EMPLOYEE STOCK                  500,000 shares          $7.755               $ 3,877,500          $ 969.38
   PURCHASE PLAN
     Class A Common Stock,
     $0.005 par value
---------------------------------- ------------------- --------------------- ---------------------- ----------------

TOTAL                               1,500,000 shares                              $11,632,500          $2,908.13
================================== =================== ===================== ====================== ================
</TABLE>

(1)  Pursuant  to  Rule  416,  this  Registration   Statement  also  covers  any
additional  shares of Class A Common  Stock  which may be  issuable  pursuant to
the antidilution  provisions of the Transaction  Systems  Architects,  Inc. 1999
Stock Option Plan or Transaction  Systems  Architects,  Inc. 1999 Employee Stock
Purchase Plan.

(2)  Estimated   solely  for  purposes  of  calculating  the   registration  fee
pursuant  to Rule 457 (c) and (h).  The price is based  upon the  average of the
high and low  prices of  Transaction  Systems  Architects,  Inc.  Class A Common
Stock on April 23, 2001, as reported on the National  Association  of Securities
Dealers Automated Quotations system.

<PAGE>
                              EXPLANATORY STATEMENT

     This Registration  Statement is filed pursuant to General  Instruction E to
Form S-8 by Transaction Systems  Architects,  Inc., a Delaware  corporation,  in
order to register (1) 1,000,000 shares of Class A Common Stock, which shares are
in addition to those previously  registered on a Registration  Statement on Form
S-8 (File No. 333-73027) filed with the Securities and Exchange  Commission (the
"Commission")  on February 26, 1999 and on a Registration  Statement on Form S-8
(File No.  333-33728)  filed with the  Commission on March 31, 2000 for issuance
pursuant to the Transaction Systems Architects, Inc. 1999 Stock Option Plan, and
(2)  500,000  shares of Class A Common  Stock,  which  shares are in addition to
those previously registered on the Registration  Statement on Form S-8 (File No.
333-73027)  filed with the  Commission on February 26, 1999. The contents of the
Registration  Statements  on  Form  S-8  (File  Nos.  333-73027  and  333-33728)
previously  filed with the  Commission  on February 26, 1999 and March 31, 2000,
respectively, are incorporated herein by reference.



                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

Item 8.  Exhibits

     Exhibit
     Number
     -------
        5         Opinion of Baker & McKenzie
       23.1       Consent of Arthur Andersen LLP
       23.2       Consent of Baker & McKenzie (See Exhibit 5)
       24         Power of Attorney (included in Signature Page)


<PAGE>

                                   SIGNATURES
         The  Registrant.  Pursuant to the  requirements  of the  Securities Act
of 1933,  the registrant  certifies  that it has  reasonable  grounds to believe
that it  meets  all of the  requirements  for  filing  on Form  S-8 and has duly
caused  this  Registration   Statement  to  be  signed  on  its  behalf  by  the
undersigned,  thereunto  duly  authorized,  in  the  City  of  Omaha,  State  of
Nebraska, on this 25th day of April, 2001.

                                       TRANSACTION SYSTEMS ARCHITECTS, INC.

                                       By:/s/William E. Fisher
                                          ------------------------------
                                          William E. Fisher, Chairman, Chief
                                          Executive Officer, and Director



                                POWER OF ATTORNEY

         We, the  undersigned  officers  and  directors of  Transaction  Systems
Architects,  Inc.,  hereby  severally and  individually  constitute  and appoint
William E. Fisher,  Dwight G. Hanson and David P. Stokes,  and each of them, the
true and  lawful  attorneys  and  agents of each of us to  execute  in the name,
place and stead of each of us  (individually  and in any capacity  stated below)
any and all  amendments  to this  Registration  Statement  on Form S-8,  and all
instruments  necessary  or advisable in  connection  therewith,  and to file the
same with the  Securities  and Exchange  Commission,  each of said attorneys and
agents to have  power to act with or  without  the other and to have full  power
and  authority  to do and  perform  in the  name  and on  behalf  of each of the
undersigned  every  act  whatsoever  necessary  or  advisable  to be done in the
premises  as fully and to all intents  and  purposes  as any of the  undersigned
might or could do in person,  and we hereby  ratify and confirm  our  signatures
as they may be signed by our said  attorneys  and agents and each of them to any
and all such amendments and other instruments.

         Pursuant  to the  requirements  of the  Securities  Act of  1933,  this
Registration  Statement  has  been  signed  by  the  following  persons  in  the
capacities and on the date indicated.
<TABLE>
<CAPTION>

Name                                        Title                                                Date
----                                        -----                                                ----
<S>                                         <C>                                                  <C>

/s/ William E. Fisher                       Chairman, Chief Executive                            April 25, 2001
----------------------------                Officer and Director
   William E. Fisher

/s/ Dwight G. Hanson                        Chief Financial Officer                              April 25, 2001
----------------------------                and Senior Vice President
   Dwight G. Hanson

/s/ Edward C. Fuxa                          Controller                                           April 25, 2001
---------------------------
   Edward C. Fuxa

/s/ Charles E. Noell, III                   Director                                             April 25, 2001
---------------------------
   Charles E. Noell, III

/s/ Jim D. Kever                            Director                                             April 25, 2001
---------------------------
   Jim D. Kever

/s/ Larry G. Fendley                        Director                                             April 25, 2001
---------------------------
   Larry G. Fendley

/s/ Roger K. Alexander                      Director                                             April 25, 2001
---------------------------
   Roger K. Alexander

/s/ Gregory J. Duman                        Director                                             April 25, 2001
---------------------------
   Gregory J. Duman
</TABLE>

<PAGE>


                                  EXHIBIT INDEX

Exhibit
Number            Description
-------           ------------
      5           Opinion of Baker & McKenzie
     23.1         Consent of Arthur Andersen LLP
     23.2         Consent of Baker & McKenzie (See Exhibit 5)
     24           Power of Attorney (included in Signature Page)
[{"type": "S-8", "sequence": "1", "filename": "s8esppstockoption.txt", "description": "1999 ESPP & STOCK OPTION PLANS", "secsgml_size_bytes": 9866}]
{"company-data": {"conformed-name": "TRANSACTION SYSTEMS ARCHITECTS INC", "cik": "0000935036", "assigned-sic": "7372", "irs-number": "470772104", "state-of-incorporation": "DE", "fiscal-year-end": "0930"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-59630", "film-number": "1612540"}, "business-address": {"street1": "224 SOUTH 108TH AVE", "city": "OMAHA", "state": "NE", "zip": "68154", "phone": "4023907600"}, "mail-address": {"street1": "224 SOUTH 108TH", "city": "OMAHA", "state": "NE", "zip": "68154"}}
================================================================================

     As filed with the Securities and Exchange Commission on April 27, 2001

                                               Registration No. 333-____________

                UNITED STATES SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                    FORM S-8

             REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933
                                _________________

                      TRANSACTION SYSTEMS ARCHITECTS, INC.
             (Exact name of registrant as specified in its charter)

              Delaware                              47-0772104
    (State or other jurisdiction of      (I.R.S. Employer Identification No.)
     incorporation or organization)

                             224 South 108th Avenue
                              Omaha, Nebraska 68154
          (Address of principal executive offices, including zip code)
                                _________________

           Transaction Systems Architects, Inc. 1999 Stock Option Plan
     Transaction Systems Architects, Inc. 1999 Employee Stock Purchase Plan
                            (Full title of the plans)

                              David P. Stokes, Esq.
                          General Counsel and Secretary
                      Transaction Systems Architects, Inc.
                             224 South 108th Avenue
                              Omaha, Nebraska 68514
                                 (402) 334-5101
(Name, address and telephone number, including area code, of agent for service)
CALCULATION OF REGISTRATION FEE

================================== =================== ===================== ====================== ================
                                                         Proposed Maximum      Proposed Maximum        Amount of
                                      Amount to be      Offering Price Per    Aggregate Offering     Registration
    Title of Securities to be        Registered (1)         Share (2)                Price                Fee
           Registered
================================== =================== ===================== ====================== ================
1999 STOCK OPTION PLAN              1,000,000 shares         $7.755               $ 7,755,000          $1,938.75
     Class A Common Stock,
     $0.005 par value
---------------------------------- ------------------- --------------------- ---------------------- ----------------

1999 EMPLOYEE STOCK                  500,000 shares          $7.755               $ 3,877,500          $ 969.38
   PURCHASE PLAN
     Class A Common Stock,
     $0.005 par value
---------------------------------- ------------------- --------------------- ---------------------- ----------------

TOTAL                               1,500,000 shares                              $11,632,500          $2,908.13
================================== =================== ===================== ====================== ================
(1)  Pursuant  to  Rule  416,  this  Registration   Statement  also  covers  any
additional  shares of Class A Common  Stock  which may be  issuable  pursuant to
the antidilution  provisions of the Transaction  Systems  Architects,  Inc. 1999
Stock Option Plan or Transaction  Systems  Architects,  Inc. 1999 Employee Stock
Purchase Plan.

(2)  Estimated   solely  for  purposes  of  calculating  the   registration  fee
pursuant  to Rule 457 (c) and (h).  The price is based  upon the  average of the
high and low  prices of  Transaction  Systems  Architects,  Inc.  Class A Common
Stock on April 23, 2001, as reported on the National  Association  of Securities
Dealers Automated Quotations system.
EXPLANATORY STATEMENT

     This Registration  Statement is filed pursuant to General  Instruction E to
Form S-8 by Transaction Systems  Architects,  Inc., a Delaware  corporation,  in
order to register (1) 1,000,000 shares of Class A Common Stock, which shares are
in addition to those previously  registered on a Registration  Statement on Form
S-8 (File No. 333-73027) filed with the Securities and Exchange  Commission (the
"Commission")  on February 26, 1999 and on a Registration  Statement on Form S-8
(File No.  333-33728)  filed with the  Commission on March 31, 2000 for issuance
pursuant to the Transaction Systems Architects, Inc. 1999 Stock Option Plan, and
(2)  500,000  shares of Class A Common  Stock,  which  shares are in addition to
those previously registered on the Registration  Statement on Form S-8 (File No.
333-73027)  filed with the  Commission on February 26, 1999. The contents of the
Registration  Statements  on  Form  S-8  (File  Nos.  333-73027  and  333-33728)
previously  filed with the  Commission  on February 26, 1999 and March 31, 2000,
respectively, are incorporated herein by reference.

                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

Item 8.  Exhibits

     Exhibit
     Number
     -------
        5         Opinion of Baker & McKenzie
       23.1       Consent of Arthur Andersen LLP
       23.2       Consent of Baker & McKenzie (See Exhibit 5)
       24         Power of Attorney (included in Signature Page)
SIGNATURES
         The  Registrant.  Pursuant to the  requirements  of the  Securities Act
of 1933,  the registrant  certifies  that it has  reasonable  grounds to believe
that it  meets  all of the  requirements  for  filing  on Form  S-8 and has duly
caused  this  Registration   Statement  to  be  signed  on  its  behalf  by  the
undersigned,  thereunto  duly  authorized,  in  the  City  of  Omaha,  State  of
Nebraska, on this 25th day of April, 2001.

                                       TRANSACTION SYSTEMS ARCHITECTS, INC.

                                       By:/s/William E. Fisher
                                          ------------------------------
                                          William E. Fisher, Chairman, Chief
                                          Executive Officer, and Director

                                POWER OF ATTORNEY

         We, the  undersigned  officers  and  directors of  Transaction  Systems
Architects,  Inc.,  hereby  severally and  individually  constitute  and appoint
William E. Fisher,  Dwight G. Hanson and David P. Stokes,  and each of them, the
true and  lawful  attorneys  and  agents of each of us to  execute  in the name,
place and stead of each of us  (individually  and in any capacity  stated below)
any and all  amendments  to this  Registration  Statement  on Form S-8,  and all
instruments  necessary  or advisable in  connection  therewith,  and to file the
same with the  Securities  and Exchange  Commission,  each of said attorneys and
agents to have  power to act with or  without  the other and to have full  power
and  authority  to do and  perform  in the  name  and on  behalf  of each of the
undersigned  every  act  whatsoever  necessary  or  advisable  to be done in the
premises  as fully and to all intents  and  purposes  as any of the  undersigned
might or could do in person,  and we hereby  ratify and confirm  our  signatures
as they may be signed by our said  attorneys  and agents and each of them to any
and all such amendments and other instruments.

         Pursuant  to the  requirements  of the  Securities  Act of  1933,  this
Registration  Statement  has  been  signed  by  the  following  persons  in  the
capacities and on the date indicated.
Name                                        Title                                                Date
----                                        -----                                                ----
/s/ William E. Fisher                       Chairman, Chief Executive                            April 25, 2001
----------------------------                Officer and Director
   William E. Fisher

/s/ Dwight G. Hanson                        Chief Financial Officer                              April 25, 2001
----------------------------                and Senior Vice President
   Dwight G. Hanson

/s/ Edward C. Fuxa                          Controller                                           April 25, 2001
---------------------------
   Edward C. Fuxa

/s/ Charles E. Noell, III                   Director                                             April 25, 2001
---------------------------
   Charles E. Noell, III

/s/ Jim D. Kever                            Director                                             April 25, 2001
---------------------------
   Jim D. Kever

/s/ Larry G. Fendley                        Director                                             April 25, 2001
---------------------------
   Larry G. Fendley

/s/ Roger K. Alexander                      Director                                             April 25, 2001
---------------------------
   Roger K. Alexander

/s/ Gregory J. Duman                        Director                                             April 25, 2001
---------------------------
   Gregory J. Duman
EXHIBIT INDEX

Exhibit
Number            Description
-------           ------------
      5           Opinion of Baker & McKenzie
     23.1         Consent of Arthur Andersen LLP
     23.2         Consent of Baker & McKenzie (See Exhibit 5)
     24           Power of Attorney (included in Signature Page)