EX-99.CERT

I, William M. Lyons, certify that:


1. I have reviewed this report on Form N-Q of American Century Municipal Trust;


2. Based on my knowledge, this report does not contain any untrue statement of a
material fact or omit to state a material fact  necessary to make the statements
made, in light of the  circumstances  under which such statements were made, not
misleading with respect to the period covered by this report;


3. Based on my knowledge,  the schedules of investments  included in this report
fairly present in all material  respects the investments of the registrant as of
the end of the fiscal quarter for which the report is filed;


4.  The  registrant's  other  certifying  officer  and  I  are  responsible  for
establishing and maintaining  disclosure  controls and procedures (as defined in
Rule 30a-3(c) under the  Investment  Company Act of 1940) for the registrant and
have:


(a) Designed such disclosure controls and procedures,  or caused such disclosure
controls and  procedures to be designed  under our  supervision,  to ensure that
material  information  relating to the  registrant,  including its  consolidated
subsidiaries, is made known to us by others within those entities,  particularly
during the period in which this report is being prepared;


(b) Not  applicable  prior to the first report on Form N-Q  following  the first
annual  report on Form N-CSR for a fiscal year ending on or after  November  15,
2004;


(c) Evaluated the  effectiveness  of the  registrant's  disclosure  controls and
procedures and presented in this report our conclusions  about the effectiveness
of the disclosure controls and procedures,  as of a date within 90 days prior to
the filing date of this report, based on such evaluation; and


(d)  Disclosed in this report any change in the  registrant's  internal  control
over  financial  reporting  that occurred  during the  registrant's  most recent
fiscal  quarter  that  has  materially  affected,  or is  reasonably  likely  to
materially affect, the registrant's  internal control over financial  reporting;
and


5.  The  registrant's  other  certifying  officer  and I have  disclosed  to the
registrant's  auditors  and the audit  committee  of the  registrant's  board of
directors (or persons performing the equivalent functions):


(a) All  significant  deficiencies  and  material  weaknesses  in the  design or
operation of internal  control over  financial  reporting  which are  reasonably
likely  to  adversely  affect  the  registrant's  ability  to  record,  process,
summarize, and report financial information; and


(b) Any fraud,  whether  or not  material,  that  involves  management  or other
employees who have a significant role in the registrant's  internal control over
financial reporting.


Date:  October 25, 2004


/s/ William M. Lyons
------------------------------------------
William M. Lyons
President
(principal executive officer)






I, Maryanne L. Roepke, certify that:


1. I have reviewed this report on Form N-Q of American Century Municipal Trust;


2. Based on my knowledge, this report does not contain any untrue statement of a
material fact or omit to state a material fact  necessary to make the statements
made, in light of the  circumstances  under which such statements were made, not
misleading with respect to the period covered by this report;


3. Based on my knowledge,  the schedules of investments  included in this report
fairly present in all material  respects the investments of the registrant as of
the end of the fiscal quarter for which the report is filed;


4.  The  registrant's  other  certifying  officer  and  I  are  responsible  for
establishing and maintaining  disclosure  controls and procedures (as defined in
Rule 30a-3(c) under the  Investment  Company Act of 1940) for the registrant and
have:


(a) Designed such disclosure controls and procedures,  or caused such disclosure
controls and  procedures to be designed  under our  supervision,  to ensure that
material  information  relating to the  registrant,  including its  consolidated
subsidiaries, is made known to us by others within those entities,  particularly
during the period in which this report is being prepared;


(b) Not  applicable  prior to the first report on Form N-Q  following  the first
annual  report on Form N-CSR for a fiscal year ending on or after  November  15,
2004;


(c) Evaluated the  effectiveness  of the  registrant's  disclosure  controls and
procedures and presented in this report our conclusions  about the effectiveness
of the disclosure controls and procedures,  as of a date within 90 days prior to
the filing date of this report, based on such evaluation; and


(d)  Disclosed in this report any change in the  registrant's  internal  control
over  financial  reporting  that occurred  during the  registrant's  most recent
fiscal  quarter  that  has  materially  affected,  or is  reasonably  likely  to
materially affect, the registrant's  internal control over financial  reporting;
and


5.  The  registrant's  other  certifying  officer  and I have  disclosed  to the
registrant's  auditors  and the audit  committee  of the  registrant's  board of
directors (or persons performing the equivalent functions):


(a) All  significant  deficiencies  and  material  weaknesses  in the  design or
operation of internal  control over  financial  reporting  which are  reasonably
likely  to  adversely  affect  the  registrant's  ability  to  record,  process,
summarize, and report financial information; and


(b) Any fraud,  whether  or not  material,  that  involves  management  or other
employees who have a significant role in the registrant's  internal control over
financial reporting.


Date:  October 25, 2004



/s/ Maryanne L. Roepke
--------------------------------------
Maryanne L. Roepke
Sr. Vice President, Treasurer, and
Chief Accounting Officer
(principal financial officer)