This report presents a classification of the verbs of Zenzontepec Chatino (ZEN) based on which allomorphs of the aspect markers they select. The selection of aspect markers is determined by the semantics of the verbs, derivational morphology, and phonological factors. Before now, aspect marking in Chatino has proven opaque because previously documented varieities have undergone considerable phonological and morphological reduction, wiping out some of the earlier patterns. ZEN, on the other hand, is conservative in this respect. There are three verb classes, each with a few sub-classes, and they line up well with the verb classes that Kaufman (1993) has proposed for Proto-Zapotec. In addition to describing the verb class system for ZEN in synchronic terms, this study provides insight into the Proto-Zapotecan verb class system and documents in Chatino several derivational morphemes reconstructed for Proto-Zapotec, proving that they are of Proto-Zapotecan vintage. / text