This thesis is in two parts. The introduction begins with an examination of the myths of Rhesus and Dolon which are independent of Iliad 10. It concludes that the author knew of these and adapted parts of them. The section on authenticity summarises those features of Rh. which have been regarded by scholars as incompatible with Euripidean authorship, as well as some evidence which has previously been ignored. It concludes that a combination of unusual features in Rh. point away from the play being an early work of E. In particular, these are: a limited use of colloquialism; the absence of περi and the scarcity of απo the lameness of many of the repetitions; intertextual allusions to other tragic texts; enjambement between strophe and antistrophe at 350-351; the presence of two sets of separated strophes and antistrophes; the delivery of a lyric monody by the deus ex machina; a preference for shorter periods in anapaests than E.; the absence of a dramatic exposition; the unannounced symmetrical entries at 264; physical contact between actor and chorus at 681; the appearance of two dei ex machina; the realistic role of the chorus and the absence of any intellectual or emotional dimension. I believe that Rh. was written after the death of E. , but have found no evidence to suggest who wrote it. The introduction concludes with a brief survey of the textual sources. The commentary is based on J. Diggle's text (1994), although some other readings or conjectures have been preferred. New conjectures have been introduced at 4-5 and 247. It is the first commentary written on lines 1-526 since that of W.H. Porter (1929₂) and follows the standard format except that the lyric schemata are examined in the introduction. The anapaestic opening is defended and a αττ. λεγ is reported for the first time at 353.