Surgical reconstruction of maxillectomy defects has been described as an alternative to prosthetic rehabilitation to close the oral cavity. Advancements in microvascular surgical techniques require comprehensive treatment planning guidelines for functional rehabilitation. This retrospective study evaluated acquired maxillectomy defects after surgical reconstruction and/or prosthodontic rehabilitation in an attempt to establish surgical and prosthodontic guidelines that could be organized into a classification system. Forty-seven consecutive patient treatments of palatomaxillary reconstruction at a single facility, The Mount Sinai Medical Center (New York, N.Y.), were reviewed. All patients were rehabilitated with a tissue-borne obturator, a local advancement flap, a fasciocutaneous free flap, or a vascularized bone-containing free flap. Palatomaxillary defects were divided into 3 major classes and 2 subclasses. The aim of this defect-oriented classification system was to organize and define the complex nature of the restorative decision-making process for the maxillectomy patient.