Fermentation of Streptomyces hygroscopicus var. crystallogenes, the copiamycin source, yielded several minor components with antifungal activity. One of these minor components, neocopiamycin A, was isolated and characterized. The structure of neocopiamycin A was determined as N-demethylcopiamycin on the basis of spectroscopic evidence. The antibiotic was found to be more active against Gram-positive bacteria and fungi but less toxic than copiamycin.