Thirteen patients with cytologically or histologically confirmed ascites from various malignancies have received 37 courses of intraperitoneal cis-platinum (cDDP). The tumor had to be confined to the peritoneal cavity or cause major symptoms by peritoneal carcinosis. cDDP (90-150 mg/m2 in 21 saline) was administered intraperitoneally with concurrent i.v. infusion of sodium thiosulfate. Courses were repeated in 4-week intervals. Total platinum was assayed by flameless atomic absorption spectrophotometry. With a dwell of 4 h 31.5 +/- 17.2% of platinum was recovered. Mean peak platinum concentration in the peritoneal cavity was 54.6 +/- 21 micrograms/ml and that in serum was 2.6 +/- 1.1 micrograms/ml. The ratio of peritoneal to serum platinum concentration dropped from 41 +/- 18.2 after 1 h to 6.9 +/- 4.7 after 5 h. The area under the curve for the peritoneum was approximately 11-fold greater than the area under the curve for serum. Within 12 h 31.7 +/- 10.7% of the administered dose was excreted in urine. Ten patients had disappearance of ascites lasting 6-135 + weeks. The treatment was generally well tolerated, no serious side effects were observed. This study demonstrates a pharmacokinetic advantage of intraperitoneal chemotherapy with cDDP and an effectiveness against peritoneal carcinosis from various malignancies with minimal systemic toxicity.