The benign cementoblastoma is a rare odontogenic tumor that tends to occur in the jaws of young people. It is most commonly characterized as a circumscribed radiopaque mass attached to the tooth roots and rimmed by a thin radiolucent zone. Early lesions, however, are radiolucent and can be confused with periapical conditions resulting from nonvital teeth. The tumor is seldom recognized until it produces pain or expansion of the jaw. If the diagnosis is established early, the tooth can be saved by endodontic treatment followed by apical root resection and surgical enucleation of the tumor. This case report documents the origin, development, and unlimited growth potential of a cementoblastoma. Radiographs taken at yearly intervals reveal an initial widening of the periodontal ligament space that grew into a 3-cm mixed radiolucent and radiopaque tumor over a 4-year period. The differential diagnosis and some criteria to help distinguish the cementoblastoma from similar-appearing lesions are reviewed.