Expecting that the different characteristics of rice plants against rice blast fungus, that is, susceptibility of the weaker cultivar, Sasanishiki and resistance of the stronger cultivars, Fukuyuki and Fukunishiki, may be due to the absence or presence of anti-fungus compounds in the rice plants, the anti-rice blast fungus substances in these three kinds of rice plants were explored. We found five epoxides and five allyl alcohols as anti-rice blast fungus compounds. The epoxides were 12,13-epoxy- and 9,10-epoxylinoleic acids, and 15,16-epoxy-, 12,13-epoxy-, and 9,10-epoxylinolenic acids. The allyl alcohols are 13-hydroxy and 9-hydroxy linoleic acids, and 16-hydroxy, 13-hydroxy, and 9-hydroxy linolenic acids. In inoculated Sasanishiki, the activity is due to the formation of the allyl alcohols.