Nonspecific thickening of the apical visceral pleura and subpleural lung associated with fibrosis and sometimes with calcification, was found in 20.3% of cases. This thickening could not be shown histologically to be the result of tuberculosis. The frequency of such scarring increased significantly with age. Such localized pleural thickening may be related to healing of pulmonary disease in the presence of chronic ischemia. This subpleural scarring appears to be the cause of the apical cap shadow reported by many authors; other possibilities include (a) irregular projection of the lung into the overlying soft tissues and (b) other apical pulmonary disease.