Twenty-three chemicals out of seventy-two were found to be toxic to snails, O. nosophora, the intermediate host of Schistosoma japonicum.It seems that there is no special formula for molluscicides, but there is some specificity of substituted atom and their position in each derivative group.Trichlorophenol, pentachlorophenol, copper salt of pentachlorophenol, chloroxylenol, p-thiocresol, p-nitraniline, thioresorcinol, p-nitrophenylethyl carbonate, 3-nitro-2-aminotoluene showed remarkable molluscicidal results, and seem to be practically applicable.