Fourteen forms of endopolygalacturonases were purified from the culture medium of Sclerotinia sclerotiorum with ion exchange chromatographies. Individual forms differ in their isoelectric point but exhibit similar molecular masses, On the basis of the cross-reactions to antibodies raised against a purified acidic endopolygalacturonase, these forms could be divided into two related groups, Polygalacturonase activities constitute a complex enzyme system in which the extensive multiplicity is due to the expression of a large gene family.