Marcellus of Ancyra (c. AD 285/290 - 374) was one of the prominent bishops who fought against the Eusebians at the Council of Nicaea. After this council, he was first to attack them, and especially Asterius of Cappadocia. Only fragments of his work were preserved. These fragments, together with a letter which he wrote in AD 341 to Julius of Rome, are collected in this volume. The fragments within the collection follow the order established by K. Seibt in 1994 to give an idea of how Marcellus' work was originally structured.