Condensation of 14-bromodaunorubicin with thiols in methanol, in the presence of potassium carbonate, resulted in the formation of 14-thia analogues of the antitumor antibiotic adriamycin. However, similar condensation of N-(trifluoroacetyl)-14-iododaunorubicin with thiols invariably led to a redox reaction, with the formation of N-(trifluoroacetyl)daunorubicin and disulfides. Accordingly, N-(trifluoroacetyl)-14-bromodaunorubicin was used for reaction with thiols to yield thia analogues of the clinically active but non-DNA-binding adriamycin analogue N-(trifluoroacetyl)adriamycin 14-valerate (AD 32). Reaction of 14-bromoadunorubicin with alpha, omega-alkanedithiols gave bis(thiaadriamycin) analogues as potential difunctional intercalating agents. The aforementioned products, plus two related phenylselena derivatives, were examined for in vitro growth inhibition, in vivo antitumor activity, and, where appropriate, DNA binding. A number of agents, most notably 14-(carbethoxymethyl)-14-thiaadriamycin and N-(trifluoroacetyl)-14-phenyl-14-selenaadriamycin, were active against murine L1210 leukemia in vivo. Several of the amino glycoside unsubstituted 14-thiaadriamycin analogues exhibited DNA-binding properties equivalent to those of adriamycin.