Due to the known association with asbestos exposure, malignant mesothelioma has assumed an importance out of proportion to its incidence in the American population (2.2 per million). Patients present with chest pain, shortness of breath, or both. The initial chest X-ray generally reveals a large unilateral pleural effusion. A large piece of tissue obtained via open biopsy is usually required for histologic diagnosis. Investigational approaches include multiple needle biopsies obtained for electron microscopy, as well as for immunoperoxidase staining for keratin and CEA. The tumor characteristically remains localized until late in its course. The treatment of mesothelioma remains unsatisfactory. However, anecdotes report long-term disease-free survival after intensive treatment. Palliation with a response rate of up to 30% to various chemotherapeutic regimens has been reported by a number of investigators.