A case of peritoneal mesothelioma discovered during laparotomy for ascites is reported. A long-term survival of 5 years was observed with combined treatment: surgery and chemotherapy. Peritoneal mesothelioma is a rare neoplasm often related to asbestos exposure and its prognosis is poor. No laboratory test other than histologic examination is specific for the diagnosis. Combined treatment with radiotherapy and chemotherapy seems to improve the survival rate.