A new antibiotic complex has been obtained from the cultures of an actinomycete, strain FA-1180, isolated from a soil sample collected at lake side of Biwa in Japan. On the basis of taxonomic studies the producing microorganism is designated as Actinomadura roseoviolacea var. biwakoensis nov. var. The antibiotic complex belongs to the class of anthracycline glycoside antibiotics. All components form deep red fine needles on crystallization; components are named rubeomycin A, A1, B and B1. These components exhibit activity against Gram-positive bacteria as well as Yoshida sarcoma cell in vitro. These components are also effective on P388 leukemia.