An antagonistic fungus to Valsa ceratosperma was isolated from soil, and identified as Fusarium solani. The fungus was found to produce at least two antifungal substances in stationary culture. These, two substances were isolated from their culture filtrate as chromatographically homogeneous, amorphous solids. Their examined physico-chemical properties appeared to be identical with cyclosporin A and' C, obtained from the fermentation broth of Trichoderma polysporum, and they showed a pronounced inhibitory effect on growth of V. ceratosperma.