In the course of our screening program for new broad-spectrum antibiotics, mainly active against Gram-positive bacteria, it was found that Streptomyces strain No. B2847, isolated from a soil sample collected in Tokyo, Japan, produced such an antibiotic. The antibiotic was isolated and named tolypomycin Y. It is effective against experimental staphylococcal infection in mice with no significant toxicity. The strain is a mesophilic streptomycete and forms many characteristic sclerotic granules, which originate from aerial mycelia, on most agar media. Morphological, cultural and physiological properties were investigated and compared with those of known species. As a result, strain B2847 was considered to represent a new species and the name Streptomyces tolypophorus nov. sp. proposed. In this report the morphological, physiological and cultural characteristics of Streptomyces tolypophorus are presented.