The Praecepta Tonica by John of Alexandria (5th–6th cent. AD) ranks beside Pseudo-Arcadius’ epitome as one of the two most important surviving epitomes of Herodian’s monumental De Prosodia Catholica: it is a particularly rich depository of well-argued teaching on ancient Greek accentuation, and constitutes an indispensable tool for the reconstruction of Herodian’s work. However, despite its importance, it is available only in a seriously flawed edition prepared by Karl Wilhelm Dindorf in 1825.This edition by Georgios Xenis offers an authoritative new critical text based on a thorough examination of not only the direct and indirect witnesses, but also of some special sources of evidence. These include authors such as Michael Syncellus and Theognostus who, although they did not use John himself, drew directly on John’s source, thereby providing parallel material that serves to fill gaps in John’s textual tradition. In addition, the critical text benefits from conjectural emendation, deriving either from the editor’s own activity or from his predecessors. The division of the text into thematically coherent sections brings out its logical structure and renders it more readable, while the rich collection of parallel passages places it in its grammatical context. Exhaustive indices are provided at the end of the volume.The edition will be an invaluable resource for those engaged in critical editions of Greek authors, and will be of interest to classicists and/or linguists working on Aelius Herodian, John of Alexandria, Greek accentuation, or Greek scholarship.