We report the observation of oscillations in the superconducting transition temperature {ital T}{sub {ital c}} of Nb/Gd/Nb trilayers as the Gd layer thickness {ital d}{sub Gd} is varied. The {ital T}{sub {ital c}} minimum occurs at {ital d}{sub Gd}{approx_equal}13 A. The results are consistent with our previous study of Nb/Gd multilayers and are in support of the theoretical prediction of a {pi}-phase junction in superconductor/ferromagnet/superconductor systems. {copyright} {ital 1996 The American Physical Society.}