In continuing chemical studies of metabolites produced by the fungi belonging to the genus Pyricularia, a new phytotoxic metabolite named pyrichalasin H (1) was isolated from the fungus Pyricularia grisea (Cooke) Saccardo IFO 7287. Pyrichalasin H was found to strongly inhibit the growth of rice seedlings and at 1 μg/ml (1.9×10⁻⁶ M), characteristic curling of the shoot was observed as shown in Fig. 1. In this communication, the isolation and structural determination of pyrichalasin H is reported.