On the basis of 5 personal cases with illustrations and a review of the literature, the authors emphasize the clinicopathological features of peritoneal mesotheliomas, rare primary tumors for which the histological diagnosis is often difficult. The classical evidence by contact with asbestos fibers is obtained in every second case only. The tumor is often associated with a pleural lesion. Ultrasound and CT currently aid in the diagnosis, usually in a context of extensive ascites. The prognosis is poor. For technical reasons, surgical exeresis most often remains partial in the diffuse forms. Chemotherapy is rarely effective.