A 65-year-old man had a right-sided pleural effusion. A thoracic CT scan revealed diffuse pleural thickening resembling malignant mesothelioma. Repeated needle biopsies did not yield a definitive diagnosis. At autopsy, diffuse pleural thickening was found, and examination of a specimen of lung tissue showed large-cell carcinoma. Hyalinized fibrous tissue with malignant cell infiltration was seen in the thickened pleural tissue and metastatic pleuritis was diagnosed. Large-cell carcinoma of the lung should be considered in the differential diagnosis of pleural thickening.