Four cases of small cell carcinoma characterized by a striking involvement of the pleural sheets were investigated. The patients, four adult males with a long history of cigarette smoking, presented with symptoms common to pleural tumors, including cough and chest pain. Malignant cells were identified in pleural effusions of all cases and in the bronchial aspirate of one patient. Antitumoral treatments included chemo- and/or radiotherapy. Survival ranged from three to 17 months. At autopsy, the serosal sheets resulted to be extensively involved by thick tumor rinds, associated with massive hilar metastases. Histologically, the tumors were composed of small epithelial cells, expressing carcinoembryonic antigen and keratins and occasionally neuroendocrine markers. Our findings indicate that small cell carcinoma should be added to the group of pseudomesotheliomatous lung carcinomas and, above all, that it deserves distinction from ordinary mesothelioma, especially the small cell variant, because of its medico-legal implications and possible antitumoral treatment.