Malignant pleural mesothelioma may be composed of sarcomatous, epitheliomatous or mixed cell types. They can be differentiated from localized, benign mesothelioma. Malignant pleural mesothelioma is a rapidly fatal tumor that poses serious diagnostic and therapeutic problems. A series of 19 cases was compiled at the North Carolina Baptist Hospital, and data from these cases were compared to those of other series. The average survival time was 10 months. The most common symptoms were dyspnea, chest pain, pleural effusion, and weight loss. Three patients had a definite history of exposure to asbestos; in 6 more there was a questionable exposure. The most helpful investigative screening tool was the chest roentgenogram, in that it demonstrated an intrathoracic abnormality; however, mesothelioma could not be differentiated from inflammatory reaction or bronchogenic carcinoma with pleural effusion. Sputum cytology as well as pleural effusion cytology was only suggestive of malignancy. Bronchoscopy was not helpful. Needle biopsy yielded malignant cells in 3 of 8 patients. Exploratory thoracotomy was the most accurate means of diagnosis but was frequently followed by seeding into the incision and severe, intractable incisional pain. Therapy proved to be palliative at best. Thoracotomy did not alter the course of the disease; in fact, the production of severe incisional pain was deleterious to the patient's well-being. Cordotomy done in 3 patients brought no relief. Neither radiation therapy nor chemotherapy had a significant effect on survival time or palliation.