We describe the enucleation of large radicular cysts to the maximum extent, and their treatment based on the concept of marsupialization and drainage after apicoectomy. Marsupialization requires a long period for healing, imposing a burden on the patient with regard to postoperative management. Considering this, together with the difficulty involved in the clinical diagnosis of radicular cysts, curettage of the cyst wall and drainage may be more effective for facilitating the healing process than use of marsupialization alone.