A description of a prototype optical-digital system for automatic processing of chest X-rays and preliminary results are presented. The system consists of a digital image scanner used for locating the lung fields and texture measurements, a diffraction pattern sampling unit which provides both annular ring and wedge samples of the Fraunhofer diffraction pattern of lung areas, and a microcomputer for control and computation of decision functions. The film is positioned by a computer-controlled film transport to provide an overall automated system. The system is currently being designed for the Appalachian Laboratory for Occupational Respiratory Diseases and will be used for screening chest X-rays of coal miners for pneumoconiosis.