Demalonylcopiamycin (1) was isolated from the mycelial cake of Streptomyces hygroscopicus var. crystallogenes. The structure was determined by the identification of 1 with alkaline hydrolysis product of copiamycin (2). The new antibiotic 11) was found to be more active against Gram-positive bacteria than copiamycin (21, while slightly more active against fungi.