A culture of a new actinomycetous species, Nocardiopsis syrinage was isolated from a soil sample. The antibiotic produced by it was named nocamycin. It accumulated in the culture fluid on cultivation of the organism in a nutrient medium containing soybean meal, glycerin, sodium chloride and calcium carbonate. Crystalline nocamycin had an antitumor effect. In inhibited by 72--73 per cent the development of an intraperitoneally implanted lymphadenosis of strain NK/LI in mice.