Selection Criteria: This systematic review included the following inclusion criteria: rapid maxillary expansion (RME) controlled clinical trials, dental arch measurements made from cephalometric radiographs and dental casts, and no surgical treatment that could affect RME effects during the evaluation period. A computerized search was performed using Medline, Medline In- Process, Lilacs, PubMed, Embase, Web of Science, and all EBM Cochrane Research Systems. The key terms used in this literature search were rapid maxillary expansion, RME, tooth or dental changes. Two authors reviewed the articles independently, and the results were compared. If there was any discrepancy, the article was reviewed by all the authors. After collecting all the abstracts, only 41 studies remained. Thirty-five were rejected for methodological reasons. Only 6 articles remained, but 2 were rejected because they did not have a long-term follow-up. Of the 4 final articles, 2 measured the changes through dental casts and 2 through radiographs. Key Study Factor: Review of studies investigating the long-term effects of RME. Main Outcome Measure: The primary outcome was the long-term dental changes (intermolar width, interpremolar width, intercanine width, arch perimeter, overjet, overbite, incisor inclination, and molar extrusion) after the treatment with RME. These changes were measured in dental casts and in radiographs. Main Results: Only 4 studies were identified, and 37 were excluded for various reasons. Among the 4 studies reviewed, 2 studies evaluated changes in dental casts: 1 in a cephalometric radiograph and 1 in a posteroanterior radiograph. No meta-analysis of findings was conducted as part of this review. The authors summarized their findings as follows: (1) a long-term maxillary intermolar width increase (3.7-4.8 mm) can be achieved; (2) maxillary intercanine width expansion was more consistent among adolescents and adults (2.2-2.5 mm); (3) there was significant gain in maxillary (6 mm) and mandibular (4.5 mm) arch perimeter in adolescents treated with RME and edgewise appliances; (4) differences in arch perimeter change with treatment before or after puberty were most likely not clinically significant; and (5) there were no vertical or anteroposterior dental changes associated with RME. Conclusions: The authors concluded that a clinically significant long-term maxillary molar width increase and arch perimeter increase can be achieved with RME. © 2011 Elsevier Inc. All rights reserved.