When grown in a defined medium containing 0.05% KBr, Saccharothrix aerocolonigenes ATCC 39243 produces a novel bromo analog of rebeccamycin. This new analog, designated bromorebeccamycin, has been isolated from the culture broth and purified by vacuum liquid chromatography and column chromatography. Spectroscopic data demonstrated that bromorebeccamycin has the same structure as rebeccamycin, except for the replacement of the two chlorine atoms by bromine atoms in the molecule. Bromorebeccamycin and rebeccamycin have a similar potency and activity against P388 leukemia in the murine model.