An isolate of Colletotrichum dematium (Pers. ex Fr.) Grove f. sp. truncata (Schw.) produced endopolygalacturonase (endo PG) in culture in response to soybean seed exudates and in infected soybean seedlings 20hr after inoculation. No other depolymerizing type of pectic enzyme was detected during fungal growth under these conditions. Endo PG from these sources had pH optimum of 5.3 and molecular weights of 42,000 Kda. Enzyme preparation from culture and infected seedlings readily macerated soybean epicotyl sections. However, by using isoelectric focusing technique, it was found that the endo PG produced by Colletotrichum dematium f. sp. truncata in response to seed excudates had a single isoelectric point (PI) of 7.3, whereas the endo PG from infected epicotyls had a major peak at Pi 7.9 and a minor peak at PI 7.3. Differences in elution patterns were observed when preparations from the two sources were purified by ion-exchange chromatography. Results of this study suggest that Colletotrichum dematium f.sp. truncata produces different forms of endo PG and that the ionic properties of the predominant form produced during pathogenesis differ from those of the single-peak form produced in culture.