In the course of our screening program for novel antimicrobial antibiotics against Pasteurella piscicida, we found that a strain of Streptomyces sp. MJ885-mF8 isolated from a soil sample collected at Suginami-ku, Tokyo, Japan, produces a new antimicrobial antibiotic, tetrodecamycin (1). In this paper we report the production, isolation, physico-chemical properties and biological properties of 1.