The case of an 18-year-old Caucasian girl with a radiolucent lesion in the area of the angle of the right side of the mandible has been presented. The pathology report was consistent with the radiographic diagnosis of a traumatic bone cyst. It is recommended that when patients have a history of trauma or surgery of the maxilla or mandible periodic apical or panoramic radiographic films should be made of the involved area. Annual or semiannual bitewing films are not satisfactory substitutes. The film must be of diagnostic quality. © 1969.