Mycelial growth of Fusaruim solani f. pisi and Fusarium oxysporum pathogenic to garden pea was retarded on the medium containing pisatin, a phytoalexin from the plant, and pisatin content of the medium decreased markedly after 30 days culture of these fungi. Pisatin was slightly inactivated by mixing it into the culture filterates of these fungi and extent of pisatin inactivation did not varied to the duration of culture. Pisatin was entirely disappeared when it was mixed with spore suspension of F. solani f. pisi.