Diffuse malignant pleural mesothelioma (DMM) is associated with a very poor prognosis and is only partially accessible to treatment. On the basis of a retrospective analysis, we made an attempt to identify possible factors that influence the prognosis. Between 1964 and 1986, 84 evaluable patients were treated: the ratio of male to female patients was 4.3:1, their average age being 58.5 +/- 11.9 (range: 21-82 years). The tumour types included 50% epithelial, 38% biphasic, and 12% mesenchymal tumours. The classification in accordance with the suggestions of Butchart revealed: I 10%, II 89%, III 0%, IV 1%. In 32% of the patients, treatment was purely symptomatic, in 42% a palliative surgical procedure with decortication of the tumour and tumour-pleurectomy was performed, while in 26% the palliative procedure was followed by adjuvant chemotherapy using doxorubicin and cisplatin. The median survival for the patients overall was 253 days. Parameters that were found not to correlate with the prognosis were: age, sex, exposure to asbestos, use of tobacco, pleural effusion, and growth behaviour in the thymus aplastic nude mouse. A significant influence was found for the histological type of the tumour and therapy administered, epithelial and biphasic tumour forms, as also surgical and combined surgical/chemotherapeutic treatment resulting in a more prolonged survival. On the basis of these results, surgical therapy should always be employed, despite the fact that there is almost always no curative option; postoperative adjuvant therapy is capable of further improving the prognosis.