EXHIBIT 99.302CERT


I, Jonathan S. Thomas, certify that:


1.   I have  reviewed this report on Form N-CSR of American  Century  Investment
     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  financial  statements,  and  other  financial
     information  included  in  this  report,  fairly  present  in all  material
     respects the financial  condition,  results of  operations,  changes in net
     assets, and cash flows (if the financial statements are required to include
     a statement  of cash flows) of the  registrant  as of, and for, the periods
     presented in this report;

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) and internal
     control over  financial  reporting (as defined in Rule  30a-3(d)  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)  Designed such internal  control over  financial  reporting,  or caused
          such internal  control over  financial  reporting to be designed under
          our  supervision,   to  provide  reasonable  assurance  regarding  the
          reliability  of financial  reporting and the  preparation of financial
          statements for external purposes in accordance with generally accepted
          accounting principles;

     (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 second
          fiscal  quarter  of  the  period  covered  by  this  report  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: May 30, 2008



/s/  Jonathan S. Thomas
------------------------------------
Jonathan S. Thomas
President
(principal executive officer)






I, Robert J. Leach, certify that:


1.   I have  reviewed this report on Form N-CSR of American  Century  Investment
     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  financial  statements,  and  other  financial
     information  included  in  this  report,  fairly  present  in all  material
     respects the financial  condition,  results of  operations,  changes in net
     assets, and cash flows (if the financial statements are required to include
     a statement  of cash flows) of the  registrant  as of, and for, the periods
     presented in this report;

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) and internal
     control over  financial  reporting (as defined in Rule  30a-3(d)  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)  Designed such internal  control over  financial  reporting,  or caused
          such internal  control over  financial  reporting to be designed under
          our  supervision,   to  provide  reasonable  assurance  regarding  the
          reliability  of financial  reporting and the  preparation of financial
          statements for external purposes in accordance with generally accepted
          accounting principles;

     (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 second
          fiscal  quarter  of  the  period  covered  by  this  report  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: May 30, 2008



/s/  Robert J. Leach
------------------------------------
Robert J. Leach
Vice President, Treasurer, and
Chief Financial Officer
(principal financial officer)