This is a complete edition with critical commentary of the Byzantine Communions in thirteenth-century manuscripts of the Asmatikon, all known sources being used. The chants concerned are the earliest known examples of Communion Chants of the Orthodox Church, and are found in a book which may go back to the rite of St Sophia at Constantinople during the tenth century-the earliest copies of which date from the thirteenth-century and come from South Italy and North Greece. Further more, there are also a few manuscripts from Kiev with text in Church Slavonic and an untranscribable musical notation. This is the first systematic transcription of the Asmatikon ever to be published.