A series of compounds is described in which one of the ethyl groups in diethylstilbestrol has been replaced by a ferrocenyl substituent. Only those derivatives incorporating phenol moieties underwent isomerisation from the Z to the E form, and some of them could be chemically oxidized to a quinone species. The compounds were less cytotoxic against hormone-independent MDA-MB-231 breast cancer cell lines than their corresponding ferrocenyl phenyl or phenol isomers in which the ferrocene and ethyl moieties are linked to the same carbon atom. The biochemical results were evaluated in conjunction with information obtained from electrochemical and chemical oxidation experiments.