Since the closing years of the19th century the two treatises of St Athanasius against Apollinaris have been regarded by some scholars as spurious. This view has been a matter of considerable debate because of its implications for the interpretation of St Athanasius' Christology. The first part of this dissertation examines the history of criticism from the end of the nineteenth century to the present, and outlines the major points of research which has to be undertaken in a re-examination of the case. Accordingly the dissertation proceeds with the examination of the External Witnesses (Part II), the Internal Evidence (Part III), the Style (Part IV), the doctrine of the Death of Christ (Part V), the doctrine of the Soul of Christ (Part VI) and finally the Christology of Athanasius and the two disputed treatises (Part VII). Particular emphasis is placed on the theological issues raised in this connection. Part V contains a re-examination of all the Athanasian texts on the Death of Christ, as well as in the two works under investigation. Part VI contains a full critical analysis of the modem scholarly debate on the Soul of Christ in Athanasius. Finally Part VII (the longest section of the dissertation) re-examines all the works of Athanasius on Christology with particular reference to the doctrine and terminology of the Incarnation. The above researches establish the conclusion that there are no fundamental problems to the traditional Athanasian paternity of the two Contra Apollinarem. The external Witnesses are many and important. The internal evidence shows that Athanasius is the possible author. The Style presents no divergencies. As for the doctrine it has been shown that it is Athanasian in outline and in many significant details