As filed with the Securities and Exchange Commission on March 31, 2000.

                        Registration No. 333-____________


                       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 (I.R.S. Employer Identification No.)
                        of incorporation or organization)

                             224 South 108th Avenue
                              Omaha, Nebraska 68154
               (Address of principal executive offices) (Zip Code)

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

                              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
================================== ========================== ===================== ================ ===============
<S>                               <C>                        <C>                   <C>              <C>
                                                                Proposed Maximum       Proposed        Amount of
    Title of Securities to be            Amount to be          Offering Price Per       Maximum       Registration
           Registered                    Registered(1)               Share             Aggregate          Fee
                                                                                    Offering Price
================================== ========================== ===================== ================ ===============
Class A Common Stock,                  1,000,000 shares          $ 26.9063 (2)        $26,906,300       $7,105.00
     $0.005 par value
================================== ========================== ===================== ================ ===============
</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.

(2)      Estimated  solely for  purposes of  calculating  the  registration  fee
pursuant  to Rule  457(h).  The price is based upon the  average of the high and
low prices of  Transaction  Systems  Architects,  Inc.  Class A Common  Stock on
March 29,  2000,  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
(the  "Company"),  in  order  to  register  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 for
issuance  pursuant  to the  Transaction  Systems  Architects,  Inc.  1999  Stock
Option  Plan.  The  contents of such  previously  filed  Registration  Statement
(File No. 333-73027) are incorporated herein by reference.


                                    PART II
               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

Item 8.  Exhibits

     Exhibit
     Number

        5         Opinion of Legal Counsel
       23         Consent of Arthur Andersen LLP
       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 31st day of March, 2000.

                                   TRANSACTION SYSTEMS ARCHITECTS, INC.

                                   By:   /s/ David C. Russell
                                   --------------------------------
                                     David C. Russell, Chief Executive
                                     Officer, President and Director


                               POWER OF ATTORNEY

         We, the  undersigned  officers  and  directors of  Transaction  Systems
Architects,  Inc.,  hereby  severally and  individually  constitute  and appoint
David C.  Russell and Dwight G.  Hanson,  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/ David C. Russell        Chief Executive Officer, President    March 31, 2000
-------------------------   and Director (Principal Executive
    David C. Russell        Officer)

/s/ William E. Fisher       Chairman of the Board and Director    March 31, 2000
-------------------------
    William E. Fisher

/s/ Dwight G. Hanson        Chief Financial Officer and           March 31, 2000
-------------------------   Senior Vice President (Principal
    Dwight G. Hanson        Financial Officer)

/s/ Edward Fuxa             Controller                            March 31, 2000
-------------------------   (Principal Accounting Officer)
    Edward Fuxa

/s/ Charles E. Noell, III   Director                              March 13, 2000
-------------------------
    Charles E. Noell, III

/s/ Jim D. Kever            Director                              March 13, 2000
-------------------------
    Jim D. Kever

/s/ Larry G. Fendley        Director                              March 13, 2000
-------------------------
    Larry G. Fendley

/s/ Roger K. Alexander      Director                              March 13, 2000
-------------------------
    Roger K. Alexander


                                 EXHIBIT INDEX

Exhibit
Number            Description

      5           Opinion of Legal Counsel
     23           Consent of Arthur Andersen LLP
     24           Power of Attorney (included in Signature Page)
[{"type": "S-8", "sequence": "1", "description": "REGISTRATION STATEMENT", "secsgml_size_bytes": 8094}]
{"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": "333-33728", "film-number": "591114"}, "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 March 31, 2000.

                        Registration No. 333-____________

                       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 (I.R.S. Employer Identification No.)
                        of incorporation or organization)

                             224 South 108th Avenue
                              Omaha, Nebraska 68154
               (Address of principal executive offices) (Zip Code)

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

                              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        Amount of
    Title of Securities to be            Amount to be          Offering Price Per       Maximum       Registration
           Registered                    Registered(1)               Share             Aggregate          Fee
                                                                                    Offering Price
================================== ========================== ===================== ================ ===============
Class A Common Stock,                  1,000,000 shares          $ 26.9063 (2)        $26,906,300       $7,105.00
     $0.005 par value
================================== ========================== ===================== ================ ===============
(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.

(2)      Estimated  solely for  purposes of  calculating  the  registration  fee
pursuant  to Rule  457(h).  The price is based upon the  average of the high and
low prices of  Transaction  Systems  Architects,  Inc.  Class A Common  Stock on
March 29,  2000,  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
(the  "Company"),  in  order  to  register  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 for
issuance  pursuant  to the  Transaction  Systems  Architects,  Inc.  1999  Stock
Option  Plan.  The  contents of such  previously  filed  Registration  Statement
(File No. 333-73027) are incorporated herein by reference.

                                    PART II
               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

Item 8.  Exhibits

     Exhibit
     Number

        5         Opinion of Legal Counsel
       23         Consent of Arthur Andersen LLP
       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 31st day of March, 2000.

                                   TRANSACTION SYSTEMS ARCHITECTS, INC.

                                   By:   /s/ David C. Russell
                                   --------------------------------
                                     David C. Russell, Chief Executive
                                     Officer, President and Director

                               POWER OF ATTORNEY

         We, the  undersigned  officers  and  directors of  Transaction  Systems
Architects,  Inc.,  hereby  severally and  individually  constitute  and appoint
David C.  Russell and Dwight G.  Hanson,  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/ David C. Russell        Chief Executive Officer, President    March 31, 2000
-------------------------   and Director (Principal Executive
    David C. Russell        Officer)

/s/ William E. Fisher       Chairman of the Board and Director    March 31, 2000
-------------------------
    William E. Fisher

/s/ Dwight G. Hanson        Chief Financial Officer and           March 31, 2000
-------------------------   Senior Vice President (Principal
    Dwight G. Hanson        Financial Officer)

/s/ Edward Fuxa             Controller                            March 31, 2000
-------------------------   (Principal Accounting Officer)
    Edward Fuxa

/s/ Charles E. Noell, III   Director                              March 13, 2000
-------------------------
    Charles E. Noell, III

/s/ Jim D. Kever            Director                              March 13, 2000
-------------------------
    Jim D. Kever

/s/ Larry G. Fendley        Director                              March 13, 2000
-------------------------
    Larry G. Fendley

/s/ Roger K. Alexander      Director                              March 13, 2000
-------------------------
    Roger K. Alexander

                                 EXHIBIT INDEX

Exhibit
Number            Description

      5           Opinion of Legal Counsel
     23           Consent of Arthur Andersen LLP
     24           Power of Attorney (included in Signature Page)