A new teleocidin-related compound named blastmycetin E (1) was isolated from Streptoverticillium blastmyceticum, and the structure was elucidated by spectroscopic evidences and chemical correlation with olivoretin E (2). Teleocidins are potent skin tumor promoters produced by actinomycetes. The last several years have seen the structure determination and total synthesis of teleocidin-related compounds because of their peculiar structure involving a nine-membered lactam ring and a complex monoterpenoid moiety. Among the teleocidin-producing actinomycetes, Streptoverticillium blastmyceticum NA34-17, which had been found to produce the Epstein-Barr virus early antigen-inducing indole alkaloids, has a characteristic feature of producing (-)-indolactam V, the biosynthetic intermediate of teleocidins, in quantity. This characteristic would be advantageous to obtain a wide variety of teleocidin-related compounds, especially biosynthetic intermediates of teleocidins. In our previous publication, we reported the isolation of blastmycetin D, a possible precursor of teleocidins. Our continuous efforts to find new teleocidin-related compounds for elucidation of teleocidin biosynthesis have recently led to the isolation of a new metabolite named blastmycetin E (1, 45 mg) from the mycelia (8 kg, wet weight) of this actinomycete. This communication deals with the structure of blastmycetin E (1) and its significance in the biosynthesis of teleocidins.