Hilary of Poitiers is perhaps the most neglected of the great Patristic theologians. In particular, there has been little detailed analysis of the biblical interpretation which provides the central strand of his theological method. His work on St. Matthew is almost the first extant commentary in the Latin West. It is analysed here, with a survey, for the first time, of the growth of the commentary as a literary from. The relation between exegesis and theological method in his later work on the Trinity and the Psalms shows the development of his techniques and their theological consequences. The concluding sections provide a critical evaluation of the role of Patristic material in contemporary theology, with reference to the still intractable problem of the precise use of the Bible in theology.