Two thousand six hundred ninety-three oral panoramic radiographs were reviewed, and thirteen (0.48 percent) displayed changes characteristic of lingual cortical defects of the mandible. The abnormalities were almost equally distributed on the right and left sides, and none occurred bilaterally. All of the patients with the defects were adult males, and none of the areas was symptomatic. In one patient the defect was determined to have been present for 7 years with no discernible radiographic change.