The preparation and cytotoxic activity of 4'-azido-3'-bromo-3'-deamino-4'-deoxydaunorubicin is described. The new compound was found to be less active in vitro than adriamycin against L1210 and the sensitive cell lines KB-3-1 and MES-SA, but retained interesting cytotoxicity against the adriamycin resistant subline KB-A1 and the multidrug resistant MES-SA/Dx5 subline.