We performed continuous hyperthermic peritoneal perfnsion (CHPP) or continuous normothermic peritoneal perfusion (CNPP) combined with cisplatin (CDDP) 300 mg/kg and mitomycin C (MMC) 30 mg/kg in an attempt to prevent peritoneal recurrence after surgery for gastric cancer. Twenty-two patients were treated with perfusion using about 10 liters of saline heated to 41 ยฐ to 42ยฐC (CHPP group); 18 patients were treated with saline heated to 37 ยฐ to 380C (CNPP group); and 18 patients underwent only gastric surgery without perfusion (control group) in a randomized control study. There were two deaths (9%) due to peritoneal recurrence in the CHPP group, four (22%) in the CNPP group, and four (22%) in the control group. The 1-, 2-, and 3-year survival rates were 95%, 89%, and 68%, in the CHPP group; 81%, 75%, and 51%, in the CNPP group; and 43%, 23%, and 23%, in the control group, respectively. There was a significant difference between the three survival curves by the log-rank test 07 < 0.01). This difference showed that CNPP and CHPP are both effective procedures for preventing peritoneal recurrence. The maximum concentrations in the perfusate of total and free CDDP with 300 mg administration were 12.2 and 10.1/~g/ml, respectively, at the end of the perfnsion, and the maximum concentrations of total and free CDDP in plasma were 2.1 and 1.0 pg/ml, respectively. The maximum concentrations of MMC in perfusate and plasma with 30 mg administration were 1.00 and 0.05/tg/ml, respectively, which are intraperitoneally cytotoxic but systemically safe concentrations.