Streptomyces sp. OCU-42815 produced several novel 1-monglycerides having C17^20 branched chain fatty acids, which were first reported their antimicrobial activities against both bacteria and fungi1'2). However, similar monoglycerides having straight chain fatty acids did not show any antimicrobial activities at the concentrations up to 100/ig/ml. 1-Monoglycerides having