Periapical radiographs were processed digitally with an image-processing system. In processed images obtained with an aperture of 100 X 100 micron 2, some radiographic information was lost because the aperture was too large for processing of periapical radiographs. Greater noise and more artifacts were also present and occasionally disturbed the interpretation. Therefore, we conclude that digital image processing of periapical radiographs is not always useful. Improvement of contrast was obtained, however, and this seemed to be effective for low-contrast radiographs.