Rapid maxillary expansion is generally contra-indicated in patients with incomplete bone formation, and is only used as an alternative in those with advanced skeletal age. In young patients, Haas and Hyrax expanders are indicated and are chosen according to requirements. In adults, an application of orthodontic-surgical techniques allows correction of transversal and other deformities, offering very acceptable and predictable results while increasing the maxillary arch perimeter to correct the posterior crossbite. However, there have been reports of related complications, such as significant hemorrhage, gingival recession, root resorption, devitalization of teeth, sinus infection, oculomotor nerve paralysis, and orbital compartment syndrome. Maxillofacial surgeons should be aware of such possible complications and that patients are fully informed. This study reviews available literature and presents a case of surgical treatment, with the aim of reviewing complications occurring during the orthognathic surgery for opening the midpalatal suture. Article published in: RGO - Rev Gaúcha Odontol., Porto Alegre, v.61, n.4, p. 615-619, out./dez., 2013.