As filed with the Securities and Exchange Commission on February 26, 1999.

                                             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
     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
================================== ========================== ===================== ================ ===============
<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
================================== ========================== ===================== ================ ===============
1999 STOCK OPTION PLAN                 1,000,000 shares       $    39.8125 (2)        $  39,812,500    $  11,067.88
     Class A Common Stock,
     $0.005 par value

---------------------------------- -------------------------- --------------------- ---------------- ---------------
1999 EMPLOYEE STOCK                      250,000 shares       $    39.8125 (2)        $   9,953,125    $   2,766.97
PURCHASE PLAN
     Class A Common Stock,
     $0.005 par value

================================== ========================== ===================== ================ ===============
TOTAL                                  1,250,000 shares                               $  49,765,625    $  13,834.84
================================== ========================== ===================== ================ ===============
</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(h). The price is based upon the average of the high and low
prices of Transaction Systems Architects,  Inc. Class A Common Stock on February
22,  1999,  as  reported  on the  National  Association  of  Securities  Dealers
Automated Quotations system.



                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

Item 3.  Incorporation of Certain Documents by Reference

         The  documents  listed in (a)  through  (c) below are  incorporated  by
reference in this registration  statement and all documents  subsequently  filed
by the  registrant  pursuant  to  Sections  13(a),  13(c),  14 and  15(d) of the
Securities  Exchange Act of 1934, as amended (the "Exchange Act"),  prior to the
filing  of a  post-effective  amendment  which  indicates  that  all  securities
offered  have been  sold or which  deregisters  all  securities  then  remaining
unsold,  shall be deemed to be  incorporated  by reference  in the  registration
statement and to be part thereof from the date of filing of such documents.

         (a)      The  registrant's  latest  annual  report  filed  pursuant  to
section 13(a) or 15(d) of the Exchange Act.

         (b)      All other  reports  filed  pursuant to Section  13(a) or 15(d)
of the Exchange  Act since the end of the fiscal year covered by the  registrant
document referred to in (a) above.

         (c)      The  description  of the class of  securities  contained  in a
registration  statement  filed under the Exchange  Act,  including any amendment
or report filed for the purpose of updating such description.


Item 6.  Indemnification of Directors and Officers.

         Section 145 of the Delaware  General  Corporation  Law provides for the
indemnification  of  officers  and  directors,  subject to certain  limitations.
The  Certificate  of  Incorporation  of the  registrant  expressly  provides for
indemnification  of an  officer or  director  made a party or  threatened  to be
made a party to  proceedings  by  reason of the fact  that  such  person  was an
officer or director.  The  Certificate  of  Incorporation  also  authorizes  the
registrant  to maintain  officer and director  liability  insurance,  and such a
policy is currently in effect.


Item 8.  Exhibits

     Exhibit
     Number

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


Item 9.  Undertakings.

         (a)      The undersigned registrant hereby undertakes:

                  1.       To file,  during any period in which  offers or sales
are being made, a post-effective amendment to this registration statement:

                  (i)      To  include  any   prospectus   required  by  Section
10(a)(3) of the Act;

                  (ii)     To  reflect  in the  prospectus  any  facts or events
arising  after the  effective  date of the  registration  statement (or the most
recent  post-effective   amendment  thereof)  which,   individually  or  in  the
aggregate,  represent a fundamental  change in the  information set forth in the
registration   statement.   Notwithstanding  the  foregoing,   any  increase  or
decrease  in  volume  of  securities  offered  (if the  total  dollar  value  of
securities  offered  would  not  exceed  that  which  was  registered)  and  any
deviation from the low or high end of the estimated  maximum  offering range may
be reflected in the form of  prospectus  filed with the  Commission  pursuant to
Rule 424(b) if, in the aggregate,  the changes in volume and price  represent no
more than a 20%  change in the  maximum  aggregate  offering  price set forth in
the  "Calculation  of  Registration  Fee"  table in the  effective  registration
statement.

                  (iii)    To include any material  information  with respect to
the  plan  of  distribution   not  previously   disclosed  in  the  registration
statement  or any  material  change  to  such  information  in the  registration
statement;

         Provided,  however,  that  paragraphs  (a)(1)(i) and  (a)(1)(ii) do not
apply if the information  required to be included in a post-effective  amendment
by those  paragraphs is contained in periodic  reports  filed by the  registrant
pursuant  to  Section  13  or  Section  15(d)  of  the  Exchange  Act  that  are
incorporated by reference in this registration statement.

                  2.       That, for the purpose of determining  any liability  
under the Act, each such  post-effective  amendment  shall be deemed to be a new
registration  statement  relating to the  securities  offered  therein,  and the
offering of such  securities at that time shall be deemed to be the initial bona
fide offering thereof.

                  3.       To  remove  from   registration  by  means  of  post-
effective  amendment any of the securities  being registered which remain unsold
at the termination of the offering.

         (b)      The  undersigned   registrant   hereby  undertakes  that,  for
purposes  of  determining  any  liability  under  the Act,  each  filing  of the
registrant's  annual  report  pursuant to Section  13(a) or Section 15(d) of the
Exchange Act (and, where  applicable,  each filing of an employee benefit plan's
annual  report   pursuant  to  Section  15(d)  of  the  Exchange  Act)  that  is
incorporated  by reference in the  registration  statement shall be deemed to be
a new registration  statement  relating to the securities  offered therein,  and
the offering of such  securities  at that time shall be deemed to be the initial
bona fide offering thereof.

         (c)      Insofar as indemnification  for liabilities  arising under the
Act may be  permitted to  directors,  officers  and  controlling  persons of the
registrant pursuant to the foregoing  provisions,  or otherwise,  the registrant
has been advised that in the opinion of the Securities  and Exchange  Commission
such  indemnification  is against  public policy as expressed in the Act and is,
therefore,  unenforceable.  In  the  event  that  a  claim  for  indemnification
against such  liabilities  (other than the payment by the registrant of expenses
incurred  or  paid  by  a  director,  officer,  or  controlling  person  of  the
registrant  in the  successful  defense of any action,  suit or  proceeding)  is
asserted by such  director,  officer or  controlling  person in connection  with
the securities being  registered,  the registrant will, unless in the opinion of
counsel  the  matter  has been  settled by  controlling  precedent,  submit to a
court of appropriate  jurisdiction the question whether such  indemnification by
it is against  public  policy as  expressed  in the Act and will be  governed by
the final adjudication of such issue.


                                   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 26th day of February, 1999.

                                      TRANSACTION SYSTEMS ARCHITECTS, INC.

                                      By:   /s/   William E. Fisher    
                                      ---------------------------------
                                        William E. Fisher, 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
William E. Fisher,  Gregory J. Duman,  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.

<TABLE>
<CAPTION>

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

/s/ William E. Fisher                     Chief  Executive  Officer,  President             February 26, 1999
William E. Fisher                         and Director
                                          (Principal Executive Officer)

/s/ Gregory J. Duman                      Chief Financial Officer                           February 26, 1999
Gregory J. Duman                          (Principal Financial Officer)

/s/ Dwight G. Hanson                      Vice President                                    February 26, 1999
Dwight G. Hanson                          (Principal Accounting Officer)

/s/ David C. Russell                      Director                                          February 26, 1999
David C. Russell

/s/ Promod Haque                          Director                                          February 26, 1999
Promod Haque

/s/ Charles E. Noell, III                 Director                                          February 26, 1999
Charles E. Noell, III

/s/ Jim D. Kever                          Director                                          February 26, 1999
Jim D. Kever

/s/ Larry G. Fendley                      Director                                          February 26, 1999
Larry G. Fendley

</TABLE>

                                  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": 14673}]
{"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": "333-73027", "film-number": "99552304"}, "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 February 26, 1999.

                                             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
     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        Amount of
    Title of Securities to be            Amount to be          Offering Price Per       Maximum       Registration
           Registered                    Registered(1)               Share             Aggregate          Fee
                                                                                    Offering Price
================================== ========================== ===================== ================ ===============
1999 STOCK OPTION PLAN                 1,000,000 shares       $    39.8125 (2)        $  39,812,500    $  11,067.88
     Class A Common Stock,
     $0.005 par value

---------------------------------- -------------------------- --------------------- ---------------- ---------------
1999 EMPLOYEE STOCK                      250,000 shares       $    39.8125 (2)        $   9,953,125    $   2,766.97
PURCHASE PLAN
     Class A Common Stock,
     $0.005 par value

================================== ========================== ===================== ================ ===============
TOTAL                                  1,250,000 shares                               $  49,765,625    $  13,834.84
================================== ========================== ===================== ================ ===============
(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(h). The price is based upon the average of the high and low
prices of Transaction Systems Architects,  Inc. Class A Common Stock on February
22,  1999,  as  reported  on the  National  Association  of  Securities  Dealers
Automated Quotations system.

                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

Item 3.  Incorporation of Certain Documents by Reference

         The  documents  listed in (a)  through  (c) below are  incorporated  by
reference in this registration  statement and all documents  subsequently  filed
by the  registrant  pursuant  to  Sections  13(a),  13(c),  14 and  15(d) of the
Securities  Exchange Act of 1934, as amended (the "Exchange Act"),  prior to the
filing  of a  post-effective  amendment  which  indicates  that  all  securities
offered  have been  sold or which  deregisters  all  securities  then  remaining
unsold,  shall be deemed to be  incorporated  by reference  in the  registration
statement and to be part thereof from the date of filing of such documents.

         (a)      The  registrant's  latest  annual  report  filed  pursuant  to
section 13(a) or 15(d) of the Exchange Act.

         (b)      All other  reports  filed  pursuant to Section  13(a) or 15(d)
of the Exchange  Act since the end of the fiscal year covered by the  registrant
document referred to in (a) above.

         (c)      The  description  of the class of  securities  contained  in a
registration  statement  filed under the Exchange  Act,  including any amendment
or report filed for the purpose of updating such description.

Item 6.  Indemnification of Directors and Officers.

         Section 145 of the Delaware  General  Corporation  Law provides for the
indemnification  of  officers  and  directors,  subject to certain  limitations.
The  Certificate  of  Incorporation  of the  registrant  expressly  provides for
indemnification  of an  officer or  director  made a party or  threatened  to be
made a party to  proceedings  by  reason of the fact  that  such  person  was an
officer or director.  The  Certificate  of  Incorporation  also  authorizes  the
registrant  to maintain  officer and director  liability  insurance,  and such a
policy is currently in effect.

Item 8.  Exhibits

     Exhibit
     Number

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

Item 9.  Undertakings.

         (a)      The undersigned registrant hereby undertakes:

                  1.       To file,  during any period in which  offers or sales
are being made, a post-effective amendment to this registration statement:

                  (i)      To  include  any   prospectus   required  by  Section
10(a)(3) of the Act;

                  (ii)     To  reflect  in the  prospectus  any  facts or events
arising  after the  effective  date of the  registration  statement (or the most
recent  post-effective   amendment  thereof)  which,   individually  or  in  the
aggregate,  represent a fundamental  change in the  information set forth in the
registration   statement.   Notwithstanding  the  foregoing,   any  increase  or
decrease  in  volume  of  securities  offered  (if the  total  dollar  value  of
securities  offered  would  not  exceed  that  which  was  registered)  and  any
deviation from the low or high end of the estimated  maximum  offering range may
be reflected in the form of  prospectus  filed with the  Commission  pursuant to
Rule 424(b) if, in the aggregate,  the changes in volume and price  represent no
more than a 20%  change in the  maximum  aggregate  offering  price set forth in
the  "Calculation  of  Registration  Fee"  table in the  effective  registration
statement.

                  (iii)    To include any material  information  with respect to
the  plan  of  distribution   not  previously   disclosed  in  the  registration
statement  or any  material  change  to  such  information  in the  registration
statement;

         Provided,  however,  that  paragraphs  (a)(1)(i) and  (a)(1)(ii) do not
apply if the information  required to be included in a post-effective  amendment
by those  paragraphs is contained in periodic  reports  filed by the  registrant
pursuant  to  Section  13  or  Section  15(d)  of  the  Exchange  Act  that  are
incorporated by reference in this registration statement.

                  2.       That, for the purpose of determining  any liability  
under the Act, each such  post-effective  amendment  shall be deemed to be a new
registration  statement  relating to the  securities  offered  therein,  and the
offering of such  securities at that time shall be deemed to be the initial bona
fide offering thereof.

                  3.       To  remove  from   registration  by  means  of  post-
effective  amendment any of the securities  being registered which remain unsold
at the termination of the offering.

         (b)      The  undersigned   registrant   hereby  undertakes  that,  for
purposes  of  determining  any  liability  under  the Act,  each  filing  of the
registrant's  annual  report  pursuant to Section  13(a) or Section 15(d) of the
Exchange Act (and, where  applicable,  each filing of an employee benefit plan's
annual  report   pursuant  to  Section  15(d)  of  the  Exchange  Act)  that  is
incorporated  by reference in the  registration  statement shall be deemed to be
a new registration  statement  relating to the securities  offered therein,  and
the offering of such  securities  at that time shall be deemed to be the initial
bona fide offering thereof.

         (c)      Insofar as indemnification  for liabilities  arising under the
Act may be  permitted to  directors,  officers  and  controlling  persons of the
registrant pursuant to the foregoing  provisions,  or otherwise,  the registrant
has been advised that in the opinion of the Securities  and Exchange  Commission
such  indemnification  is against  public policy as expressed in the Act and is,
therefore,  unenforceable.  In  the  event  that  a  claim  for  indemnification
against such  liabilities  (other than the payment by the registrant of expenses
incurred  or  paid  by  a  director,  officer,  or  controlling  person  of  the
registrant  in the  successful  defense of any action,  suit or  proceeding)  is
asserted by such  director,  officer or  controlling  person in connection  with
the securities being  registered,  the registrant will, unless in the opinion of
counsel  the  matter  has been  settled by  controlling  precedent,  submit to a
court of appropriate  jurisdiction the question whether such  indemnification by
it is against  public  policy as  expressed  in the Act and will be  governed by
the final adjudication of such issue.

                                   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 26th day of February, 1999.

                                      TRANSACTION SYSTEMS ARCHITECTS, INC.

                                      By:   /s/   William E. Fisher    
                                      ---------------------------------
                                        William E. Fisher, 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
William E. Fisher,  Gregory J. Duman,  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/ William E. Fisher                     Chief  Executive  Officer,  President             February 26, 1999
William E. Fisher                         and Director
                                          (Principal Executive Officer)

/s/ Gregory J. Duman                      Chief Financial Officer                           February 26, 1999
Gregory J. Duman                          (Principal Financial Officer)

/s/ Dwight G. Hanson                      Vice President                                    February 26, 1999
Dwight G. Hanson                          (Principal Accounting Officer)

/s/ David C. Russell                      Director                                          February 26, 1999
David C. Russell

/s/ Promod Haque                          Director                                          February 26, 1999
Promod Haque

/s/ Charles E. Noell, III                 Director                                          February 26, 1999
Charles E. Noell, III

/s/ Jim D. Kever                          Director                                          February 26, 1999
Jim D. Kever

/s/ Larry G. Fendley                      Director                                          February 26, 1999
Larry G. Fendley
EXHIBIT INDEX

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