Two lexica to Plato have survived from Antiquity: the epitome of Timaeus and the so-calledPseudo-Didymus. This is the first critical edition of these lexica relying on a complete survey of their textual traditions, both direct and indirect, which are investigated in the Italian prefaces; it is also provided with an up-to-date picture of Timaeus, with an extensive inquiry into his sources and with an analysis of the mutual relationships between the two works. The critical text is provided with a threefold apparatus and detailed indexes.