A case of monostotic, mandibular fibrous dysplasia has been described in a 22-year-old Amerasian male, who had facial asymmetry of approximately 5 years' duration. Foci of ill-defined sclerotic, pagetoid calcifications were seen on routine film. The CT scans demonstrated bone facial and slight lingual expansion of bone with thinning of the cortex. A three-dimensional, enhanced CT film showed that this lesion was greater than 4 cm. The clinical, radiologic, and microscopic features of fibrous dysplasia have been described.