Pharmacokinetic parameters after intra-peritoneal administration of low-dose cis-platinum (CDDP) were analysed in order to evaluate the possibility of applying low-dose 5-FU/CDDP therapy (1-FP) for outpatients. Four patients with advanced gastric cancer were the subjects of this study. CDDP at a dose of 20 mg/body was administered intra-peritoneally, and peripheral venous blood was collected at 30 min, 4, 8, 24, 48, 72, 96 and 120 hr after drug administration. The plasma platinum (Pt) concentration was determined by atomic absorption spectrometry. Pharmacokinetic parameters were calculated using a two-compartment open model. C max, AUC, t1/2 alpha and t1/2 beta of total-Pt were 1. 27 +/- 0.21 micrograms/ml, 95.28 +/- 16.93 micrograms.hr/ml, 1.91 +/- 0.76 hr and 190.2 +/- 125.6 hr, respectively. Total-Pt concentration at 120 hr, after administration was 0.54 +/- 0.14 microgram/ml. This result suggests that intraperitoneal low-dose CDDP administration is a promising method for 1-FP therapy for outpatients, because the plasma total-Pt level is maintained at a sufficiently high level for a long period.