In the course of screening for antifungal agents active against Candida albicans, a new antifungal antibiotic has been isolated from an actinomycete strain A-3030 and was designated TMC-34. Spectroscopic analysis revealed that TMC-34 belonged to the class of 32-membered macrolide antibiotics represented by copiamycin1'2) and neocopiamycin3). This paper describes the production, isolation, physico-chemical properties, structure elucidation and biological activity of TMC-34.