Did Tatian consult the Syriac version of the OT when drawing up his Gospel harmony? This question, first raised almost a century ago,1 has not become irrelevant since then, in spite of much progress in research on both the Diatessaron and the OT Peshitta.2 In a study of OT quotations contained in the Old Syriac and Peshitta Gospels, the present writer, following in the footsteps of F C. Burkitt and S. P. Brock, undertook to show that Tatian did make use of the OT Peshitta.3 I concluded that Tatian, in his Diatessaron, frequently inserted OT Peshitta readings as a rendering of OT quotations instead of translating the Greek text as read in the Gospels.4 This position has recently been challenged by R. Shedinger on methodological grounds: since no Western witnesses of the Diatessaron were used to show dependence on the OT Peshitta, and since Shedinger's own analysis of quotations in the Western harmonies produced no traces of such dependence, the hypothesis became, in his view, untenable.5 The present article offers a renewed survey of relevant readings. In the first section, the Eastern evidence is briefly reevaluated. As will be seen, this evidence cannot be brushed aside as easily as has been done by Shedinger. The second and third sections introduce new material from Western sources that is supportive of the hypothesis. Although the thesis of Tatianic dependence on the OT Peshitta cannot, in the absence of the original text of the Diatessaron, be proven absolutely, the conclusion must be that what textual evidence we have is strongly supportive of it. I. Traces of the Old Testament Peshitta in Eastern Witnesses of the Diatessaron Historical research shows that Tatian's harmony was probably from the start a Syriac writing.6 The impact of the work is felt primarily in the Syriac-- speaking area, while the Greek church appears to have had no firsthand knowledge of it. To prove Syriac origin on a textual basis is hard, since no complete original text of the Diatessaron has been preserved.7 It may fairly be stated, however, that the textual evidence is generally supportive of the hypothesis,8 and that no textual facts oppose it, not even the Greek fragment of the Diatessaron found in Dura Europos.9 If the Diatessaron was written in Syriac, precedence must be conceded to the Eastern sources. Although even the earliest Syriac witnesses show clear signs of having been modified later in the direction of Greek manuscripts of the Gospels, they nevertheless offer the possibility of retracing part of the wording of the Diatessaron itself. 10 The Arabic and Persian harmonies are more problematic, both because these texts are of a later date and because they are translations. But at least they depend directly on a Syriac text, whereas Western harmonies are mostly translations twice or thrice removed from the original. It is good method, therefore, to build a hypothesis regarding Tatian's sources first and foremost on the basis of the Eastern evidence. Ephrem's Commentary on the Diatessaron On the supposition of a Syriac original, the only direct witness to the text of the Diatessaron is to be found in Gospel quotations in early Syriac texts. Early Syriac authors, particularly Aphrahat and Ephrem, quote the Gospel primarily, or even exclusively, according to the Diatessaron.11 Even these quotations show us a text adapted to that of the Greek Gospels,12 but they are generally, and rightly, considered to be our best source. When Burkitt first addressed the question of the possible influence of the OT Peshitta on the Diatessaron, it is to these quotations that he turned for a solution.13 The results were disappointing. Ephrem's Commentary on the Diatessaron was then available only in an Armenian translation, which did not permit a clear conclusion; as to Aphrahat, the evidence seemed to indicate a positive answer, but it was hard to be certain.14 Returning to the problem three-quarters of a century later, Brock found himself in a much more favorable position. …