A large maxillary cyst was treated for 3 months with marsupialization and decompression, followed by surgical endodontic therapy of the affected teeth and cystectomy. Although small cystic lesions will typically heal with nonsurgical endodontic therapy, larger lesions may need additional treatment. Surgical enucleation of a large cystic lesion may lead to damage of other teeth or anatomic structures. Therefore, treatment should begin with the more conservative approach of decompression, to reduce the size of the lesion, followed by apicoectomy and cystectomy.