We have synthesized a novel platinum(II) coordination complex containing trans-ι-1,2-diaminocy-clohexane (DACH) as a carrier ligand and 1,2-dichloroethane (DCE) as a leaving group. A new series of [Pt(trans-ι-DACH)(DCE)](PC) was evaluated for its cytotoxic activity on MKN-45 human gastric adenocar-cinoma cells and normal primary cultured kidney cells. The new platinum complex has demonstrated high efficacy in the cytotoxicity against MKN-45/P, MKN-45/ADM and MKN-45/CDDP cell-lines. The cytotoxicity of PC against rabbit proximal renal tubular cells, human renal cortical cells and human renal cortical tissues, determined by MTT assay, the [$^3H$]-thymidine uptake arid glucose consumption tests, was found to be quite less than those of cisplatin. Based on these results, this novel platinum(II) coordination complex appears to be better for improving antitumor activities with low nephrotoxicity and is a valuable lead in the development of new, clinically available anticancer chemotherapeutic agents.