We report the case of a 92-year-old man with a 13-year history of occupational asbestos exposure who presented with a complaint of dyspnea. In September 2001, bilateral pleural effusions were revealed on chest radiography, and continued to progress despite treatment for heart failure. Chest CT revealed calcification of the pleura but no abnormal findings in the lung fields. Both pleural effusions were exudative and lymphocytes were the predominant cells contained in them. Antituberculous chemotherapy had no effect on the exudates. In March 2002, thoracoscopy was performed under local anesthesia (medical thoracoscopy). Plaque was recognized on the parietal pleura; however, the serosal surfaces of the parietal and visceral pleura were smooth, and no evidence of malignancy, especially malignant mesothelioma, was noted. The patient's condition was diagnosed as benign asbestos pleural effusions. Prednisolone was administered, and these effusions gradually decreased. Cases of benign asbestos pleural effusion occurring simultaneously with massive bilateral effusions are rare. Thoracoscopy aided in the differential diagnosis of this case.