Around 392 Theodore of Mopsuestia delivered his homilies to candidates for baptism. Using Theodore's homilies, this work studies the reception and influence of the Nicene Creed in the imperial church since Theodosius.Passed at Nicæa in 325 the Creed became an official dogma of the empire in 380/81. What was its role in the life of the church and in the theological controversies of the subsequent years? At which point did the people start to pay attention to its exact original wording? To which extent were Theodore's theological teachings influenced by the trinitarian dogma of Nicæa?The text of Theodore's Baptismal Creed is reconstructed in both its Syriac and Greek versions. It proves to be one of the most important sources of the Nicæno-Constantinopolitan Creed of 381.