A toxin was separated from cultural solution of Phytophthora moronis. The toxic had apparently wilting activities to seedling of Cucumis melon L. We purified the toxin with DEAE- 52 column and got two perts from it. Components
wilting activities and spectrum of flurescence of those twc parts were compared and analyses. It was discovered that function of the toxin was a main reason of causing disease in Cucumis melon L by Phtophthora melonis.