Streptovirudin is a complex of antibiotics isolated from fermentation of a Streptomyces strain. Eight components have been isolated as pure substances, designated as streptovirudins A1, A2, B1, B2, C1, C2, D1, and D2. The streptovirudins are chemically and biologically related to each other and appear to be a new family of antibiotics exhibiting activity against a variety of Gram-positive bacteria, mycobacteria, and various DNA- and RNA-viruses. According to their physico-chemical properties these antibiotics have been classified in series I and II. The streptovirudins of series II (A2, B2, C2, D2) are related to the reported antibiotics tunicamycin, mycospocidin and 24010.