Peritoneal mesothelioma is a rare malignancy that is seen in patients exposed to asbestos or in young women with no known exposure to asbestos. The clinical features of the disease are similar in these two groups, and include peritoneal carcinomatosis, ascites, thrombocytemia, systemic symptoms (fever and night sweats), and hypercoagulability. There is no known curative therapy for this disease. Cisplatin has activity in 25% of patients. Mesothelial cells are known to contain high levels of carboxylesterase, a key enzyme in the activation of Irinotecan (CPT-11) to SN-38. This retrospective review of our experience in combining cisplatin 50 or 60 mg/m2 i.v. or i.p. on day 1 with CPT-11 50 or 60 mg/m2 i.v. on day 1, 8, and 15. Courses were repeated every 4 weeks x 6. If i.p. administration of cisplatin were feasible, it was the preferred route. Response to treatment was based on RECIST criteria. Fourteen men and 3 women, median age 62 years (35-76 years) and median PS 1 (0-2) were treated. Median number of courses was two for nonresponders and six for responders. The overall response rate was 24%, but 76% of patients improved on treatment. Median survival is not reached. Grade > or = 2 side effects included anemia (n = 6), neutropenia (n = 3), nausea/vomiting (n = 4), and constipation (n = 2). Grade 1 side effects were fatigue, anorexia, weight loss, alopecia, diarrhea, neuropathy, and gastric reflux. There were no grade > or = 3 hematologic toxicities. The combination of cisplatin and CPT-11 is well tolerated and has clinical benefits in patients with peritoneal mesothelioma.