A new antibiotic complex has been isolated from cultures of Streptomyces strain No. JA 10124. On the basis of taxonomic studies, the producing microorganism is described as Streptomyces griseoflavus (Krainsky, 1914) Waksman et Henrici, 1948, subsp. thuringiensis subsp. nov., type strain JA 10124. The antibiotic complex, designated as streptovirudin, was isolated from extracts of both mycelium and culture filtrate. It is a white amorphous material which consists of ten closely related components including streptovirudins A, B, C, D and E. The streptovirudin complex exhibits antibiotic activity against Gram-positive bacteria, mycobacteria, and various DNA- and RNA-viruses.