KHPC-002[(trans-l-diaminocyclohexane-bis-1,2(diphenylphosphinoethane)platinum)·2NO₃] and KHPC-006[(cis-diaminocyclohexane-bis-1,2(diphenylphosphinoethane)platinum)·2NO₃] were synthesized as candidates for third platinum antitumor agent. Before their pharmacokinetic study, we optimized the analytical condition with HPLC and identified the major metabolites in the rat plasma. HPLC analysis by C_(18) reverse-phase column showed that standard peak of both compounds appeared rapidly at around 1 minutes, whereas metabolites of KHPC-002 and KHPC-006 which were extracted from plasma after single I.V. administration in rats or incubation for 24 hr at 37℃ showed retention time of 10∼11 minutes. These metabolites were identified as the major compound by Matrix Associated Laser Deposition/Ionization (MALDI), which only lose the 2 molecules of NO₃. Based on these results, we suggest that the major metabolites of KHPC-002 and KHPC-006 were [trans-l-diamino-cyclohexane-bis-1, 2(diphenylphosphinoethane)platinum] and [cis-diaminocyclohexane-bis-1,2(diphenylphosphinoethane)platinum], respectively.