In the course of our screening for new antibiotics, we have isolated a new member of naphthoquinone antibiotics (1, Fig. 1), from the culture broth of the strain MJ361-48F3. The antibiotic is active against Gram-positive bacteria including methicillin-resistant strain of Staphylococcus aureus (MRSA). In this communication, we report the production, isolation, physico-chemical properties, structure elucidation and biological properties of 1. The producing microorganism was isolated from a soil sample collected at Nemuro-shi, Hokkaido, Japan, which was classified as Streptomyces griseus.