Resormycin, a novel herbicidal and antifungal antibiotic, was isolated from the cultured broth of streptomycete strain. The strain was isolated from a soil collected at Yokohama-shi, Kanagawa Prefecture, Japan, and identified as Streptomyces platensis MJ953-SF5. Resormycin was purified by active charcol, Amberlite IRC-50, Amberlite CG-50 and Sephadex LH-20 column chromatographies. Resormycin markedly inhibited the growth of monocotyledonous and dicotyledonous weed. The antibiotic showed antimicrobial activity against phytopathogenic fungi.