In the course of our examination for the alkaloid productivities of Streptomyces strains, Streptomyces sp. NA-15 was found to produce a new alkaloid, pyrindicin, in the culture medium. The strain NA-15 was found to be a variant of Streptomyces griseoflavus and was designated as S. griseoflavus var. pyrindicus nov. var. After the culture conditions for pyrindicin production were studied, pyrindicin was obtained as its hydrochloride (mp 145°C, decomp.) from the cultured broth. The compound was shown to possess weak antimicrobial and several pharmacological activities. The LD50of the hydrochloride (ip, in mice) was 87 mg/kg. © 1974, Japan Society for Bioscience, Biotechnology, and Agrochemistry. All rights reserved.