In this work the three oldest translations of the Gospels into Syriac are minutely compared in five passages, one from each Gospel and one common to the Synoptics, in order to ascertain their translation methods and linguistic differences. In the conclusion, guidelines are set forth for their use in the Greek textual apparatus and the linguistic data is applied to four questions: 1) what are the sources of the linguistic anomalies in the Old Syriac, 2) when was the Old Syriac translated, 3) who translated it, 4) what is its relation to the Diatessaron.