Three gold(III)-polyamine complexes of different structure — ([Au(en)2Cl3, [AuCl(dien)]Cl2 and [Au(cyclam)](ClO4)2Cl) — were synthesized and tested for cytotoxic properties against a human tumor cell line (A2780) either sensitive (A2780/S) or resistant (A2780/R) to cisplatin. Significant cytotoxic activities were found for both [AuCl(dien)]Cl2 and [Au(en)2]Cl3, whereas [Au(cyclam)](ClO4)2Cl was poorly cytotoxic. The stability of these gold(III) complexes under physiological conditions was investigated through absorption spectroscopy; their ability to bind DNA, the presumed final target for the cytotoxic action, and modify its conformation was studied through atomic absorption and circular dichroism spectroscopies. Attempts are made to define preliminary structure-function relationships for cytotoxic gold(III) complexes.