Objectives: Epithelium at the apex of a nonvital tooth can be presumably stimulated by inflammation to form a true epithelium-lined cyst, or radicular cyst. The source of the epithelium is usually a rest of Malassez but also may be traced to sinus lining or epithelial lining of fistulous tracts. Cyst development is common; the reported frequency varies from 7% to 54% of periapical radiolucencies. The incidence of radicular cysts is greater in the third to sixth decades and shows a slight male predominance. Most of the radicular cysts are found in the maxilla, especially around incisors and canines.