The Praecepta Tonica by John of Alexandria (5th-6th cent. AD) is one of our richest sources for ancient Greek accentuation and an indispensable tool for reconstructing Herodian s famous De prosodia catholica. Despite its importance, it is available only in a seriously flawed edition brought out by Karl Wilhelm Dindorf in 1825. The newedition offers an authoritative new critical text based on a thorough review of the manuscript evidence and the modern scholarship, and includes a rich collection of parallel passages intended to place the treatise in its grammatical context."