This volume contains a new critical edition of Pseudo-Arcadius' Epitome of Herodian's De Prosodia Catholica, including an extensive introduction, critical apparatus, apparatus of parallel passages, and full commentary. Misattributed to Arcadius, this epitome is one of the two main sources for Herodian's highly influential lost work, which was the first systematic treatment of ancient Greek prosody to have a substantial and lasting impact on ancient and medieval Greek scholarship and teaching. It is also responsible to a large extent for our knowledge of the ancient rules of Greek accentuation, which we still attempt to follow today, and was also widely used by grammatical and lexicographical writers, not only on accentuation but also on a variety of other aspects of grammar. This new edition employs for the first time two manuscripts which thorough examination of all the surviving sources has revealed to be of primary importance, enabling the text to be improved to a considerable degree in comparison to earlier editions. This ground-breaking research is apparent in the apparatus of parallel passages, which contains a collection of texts that have derived material from Herodian, often enabling us to reconstruct the text of Pseudo-Arcadius' Epitome and illustrating the extent of Herodian's influence on later studies of grammar. Corrupt passages and features of the text that have never been examined before are also discussed in detail in the first full commentary on the work, cementing this edition as a definitive and authoritative contribution to modern Herodianic studies.