In the course of screening research on new insecticides among metabolites of microorganisms, two active components were isolated from mycellia of Streptomyces sp. 16-22. The names, Piericidin A and B, were proposed to these active metabolites. Isolation procedure, physical and chemical properties and physiological activities of Piericidin A were presented. From the results of taxonomic study on Streptomyces sp. 16-22, it was found that this is a new species, to which the name, Streptomyces mobaraensis Nagatsu et Suzuki, was proposed.