Several insecticides have been found among the metabolites of microorganisms,1 ~5) but only tetranactin6) is practically used as a miticidal antibiotic. We screened microbes for insecticides, and successfully obtained a strain showing insecticidal activity from a sample of soil collected in Sakai city. This strain, Streptomyces sp. AH-4, showed marked activity toward silkworms on oral administration. This paper describes the isolation and identification of the insecticidal compounds involved together with their activities.