In this article we discussed the work-up necessary to evaluate a patient for maxillary transverse deficiency, and the three treatments for maxillary transverse deficiency-SDE, RME, and SA-AME. Slow dentoalveolar expansion is used mostly in the primary and early mixed dentition. Rapid maxillary expansion is indicated most often in the mixed dentition and can be attempted in the early adult dentition. Surgically assisted-rapid maxillary expansion is applicable almost exclusively in the adult dentition. The treatment of choice will depend on the age and skeletal maturity of the patient. Surgically assisted-rapid maxillary expansion, the technique that is used at The Medical College of Pennsylvania, combines all aspects of the previously mentioned osteotomies. The maxilla is separated at the midpalatal, the maxillary buttress, and the pterygomaxillary sutures. We have experienced good outcomes and stability with this technique. The reviewed literature shows good results with SA-RME for the treatment of maxillary transverse deficiency in the adult patient. It would be beneficial to study relapse and the periodontal ramifications of maxillary expansion further to better define the indications for SDE, RME, and SA-RME.