The authors had a case of large periodontal cyst treated by Apicoectomies in 32 year old, Korean female. 1. A large periodontal cyst revealed big size in Maxilla, left side. 2. The authors have treated the periodontal cyst by means of the apicoectomies of the involved left lateral incisor, canine, 1st premolar and 2nd premolar teeth, maxilla. 3. Radiographic examination revealed a large radiolucent lesion 2.7 3.7cm in diameter, in the midline area, with involvement of the lateral incisor, canine, 1st premolar and 2nd premolar teeth, maxilla.