Use of the antitumor drug doxorubicin is limited by cardiomyopathic side-effects which are believed to be due to iron-mediated hydroxyl radical generation. Dexrazoxane reduces this cardiotoxicity, possibly by removal of iron from doxorubicin by the EDTA-like hydrolysis product of dexrazoxane, ADR-925. However, EDTA-diimides like dexrazoxane, previously used as antitumor agents, are themselves carcinogenic, and recent studies have found that Fe-ADR-925 can also promote hydroxyl radical production. This study demonstrates that, like Fe-EDTA, Fe-ADR-925 and a related desmethyl complex can cleave plasmid DNA under Fenton conditions, and suggests by radical scavenger study that this cleavage is probably via the hydroxyl radical. Differences in DNA cleavage dependence upon concentrations of Fe-EDTA, Fe-ADR-925 and Fe-EDTA-bisamide can be explained by differences in the solution chemistry of the complexes.