The lateral periodontal cyst is a relatively rare cyst of the jaw (0.8%) of unproven origin. It is most commonly found in the mandible between the roots of canines and premolars. This article reports a case of a lateral periodontal cyst in a 73-year-old woman, documents its diagnosis and treatment, and also presents a 1-year reentry. No grafting or barrier techniques were used. The result was complete bony regeneration of the defect after 1 year.