Between 1969 and 1985, 245 patients with diffuse malignant mesotheliomawere treated (157 male, 88 female). The average age was 55.8 years and thesex ratio was 1.8:1 in favour of males. The right side was more frequentlyaffected than the left (56.7% vs. 43.3%). A pleural effusion and dyspnoeawere the presenting signs and symptoms in 83.7% of the patients andunilateral chest pain in 64.2%. Noninvasive diagnostic procedures includeda chest X-ray and computed tomography of the thorax. Pleural effusion andpleural thickening were detected most frequently. Malignant cells wereidentified by pleural fluid cytology in 45.3% and by needle biopsy of thepleura in 42.7% of the patients. Forty-five patients were treatedconservatively and 200 patients underwent operation: diagnostic thoracotomy(78); partial pleurectomy (72); total pleurectomy (46); extendedpleuropneumonectomy (2); partial removal of the diaphragm (1) and totalpleurectomy and upper lobectomy (1). The perioperative mortality was 6%.The conservative and postoperative treatment depended on the patients'symptoms and included radiotherapy and chemotherapy alone or incombination. The mean survival time of the 222 non-survivors was 9.2months. After 1 year, 36% of the patients were still alive, after 2 years,10.8% and the 5- year survival was 4.1%. The median survival time inpatients treated non-operatively was 6 months--a little over half that ofthe patients treated surgically (10.1 months).