Seven novel platinum (II) complexes [Pt (II) (NH3) (CH3NH2) X-2] ( I - VII) (X: CH3COO-, CH2ClCOO-, CHCl2COO-,C6H5-COO-, p-CH3O-C6H4-COO-, p-NH2-C6H4-COO-, p-NO2-C6H4-COO-) were prepared and characterized by means of elemental analysis, molar conductivity, thermal analysis, IR, UV, and H-1 NMR spectrometries. The cytotoxicity against HCT-8, BGC-823, MCF-7, EJ, and HL-60 cell lines increases in the following sequence: cisplatin > IV > V > VI > VII > I > II > III. Moreover, the complexes ( I-VII) display substantially greater activities against EJ and HL-60 cell lines than those against the cell lines from other carcinomas. They can induce a concentration-dependent accumulation of HL-60 cells in the G(2)/M phase of the cell cycle as cisplatin. There is no significant correlation between total DNA platination levels and cytotoxicity of the complexes.