Twenty-three patients with malignant peritoneal mesothelioma seen at the Dana Farber Cancer Institute and the University of Maryland Cancer Center from 1968 to 1982 were studied to assess the natural history of the disease and the efficacy of current treatment. Asbestos exposure was reported by 57%. Of 18 patients receiving a doxorubicin-containing regimen, 14 had measurable or evaluable disease. One complete response, four partial responses and one regression (in a patient with evaluable but not measurable disease) were observed, ranging in duration from 6 to 36 months. A single patient remains disease free for more than 36 months after subsequent radiotherapy. Significant clotting abnormalities (including disseminated intravascular coagulation, massive thrombosis, fatal pulmonary emboli, Coombs-positive hemolytic anemia, and phlebitis) occurred in 22% of the patients. Trends toward decreased survival were observed for smokers, patients presenting with ascites, and those with stage II-IV disease.