The diagnosis of sclerosing osteomyelitis of Garrè, or periostitis ossificans, is suggested by a history of hard swelling of the mandible accompanied by a carious dentition. Computed tomography, nuclear medicine scanning, and pantomography are used to illustrate the appearance of this condition arising in a 25-year-old woman. The differential diagnosis of mandibular thickening and associated bony sclerosis is discussed.