Four diam(m)ineplatinum(II) complexes containing beta-phenylisosuccinate as the leaving groups were prepared, characterized, and evaluated for their cytotoxicity against A549/ATCC human lung cancer cell line and SGC-7901 human gastric cancer cell line. One of the complexes, (trans-1R,2R-diaminocyclohexane)-beta-phenylisosuccinatoplatinum(II) 4, was much more active than cisplatin and carboplatin.