Osteoma is a benign neoplasm characterized by proliferation of compact or cancellous bone. The most common sites of occurrence are the flat bones of the skull. In the maxillofacial region, the mandible is more frequently involved than the maxilla. When an osteoma occurs in the mandible, it is typically found on the lingual surface of the ramus or the inferior border of the mandible in the molar area. Other mandibular sites include the condylar and coronoid processes. A review of the literature revealed that osteomas of the glenoid fossa are extremely rare.1Attanasio R. Bavitz B.J. Cohen D. Gelline S. Prosthodontic and surgical management of a patient with an osteoma of the temporo-mandibular joint.Compend Contin Educ Dent. 1998; 19: 258-269Google Scholar This is a report of a rare case of osteoma of the glenoid fossa. Historical, clinical, histopathologic, and radiographic findings are presented. In 2003 a 44-year-old Caucasian female was referred to the Baylor College of Dentistry Oral and Maxillofacial Surgery clinic for evaluation of progressive mandibular asymmetry. She complained of facial deviation that seemed to have become more visible in the previous 2 years. Cosmetic impairment and crossbite were her main concerns. Upon clinical evaluation, the patient had a dental mandibular midline deviation of 5 mm to the left. Maximal interincisal opening was 50 mm with deviation to the left. A good mandibular range of motion was present with mild tenderness over right temporomandibular joint area upon palpation. No history of headaches, TM joint pain, or noise was elicited. Clinical examination did not reveal temporal bony protuberances, masses or changes in facial contour other than her facial asymmetry. Several radiographic studies were performed, including a panoramic projection, conventional tomography of the TM joints, CT, MRI, and bone scintigraphy. From these studies a large osseous mass of the roof of the glenoid fossa was apparent, protruding inferiorly and medially. The differential diagnosis included osteochondroma and osteoma. Corrective surgery was performed in April 2004. The histopathologic diagnosis was benign sclerotic bone, consistent with a diagnosis of osteoma. Osteoma is the second most common benign tumor of the TM joint area. However, unlike the present case, it more commonly involves the condylar process. Like osteochondroma, it is painless and slow growing, typically causing the chin to be deviated toward the unaffected side. Occlusal changes are expected.