N-CSR Item 12(a)(2) - Exhibits: Certifications


I, J. Christopher Donahue, certify that:

1.    I have reviewed this report on Form N-CSR of Federated GNMA Trust
      ("registrant");

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 officers 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 officers 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: March 23, 2006
/S/ J. Christopher Donahue
J. Christopher Donahue
President - Principal Executive Officer





   N-CSR Item 12(a)(2) - Exhibits: Certifications


I, Richard A. Novak, certify that:

1.    I have reviewed this report on Form N-CSR of Federated GNMA Trust
      ("registrant");

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 officers 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 officers 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: March 23, 2006
/S/ Richard A. Novak
Richard A. Novak
Treasurer - Principal Financial Officer