Objectives: To evaluate skeletal and dentoalveolar changes produced by the Mandibular Anterior Repostioning Appliance (MARA) in the treatment of Class II malocclusion in adolescent patients. Materials and Methods: Lateral cephalograms of 24 patients, mean age 12.40 years, with a Class II malocclusion consecutively treated with MARA were compared with a historical control group. Changes were evaluated using the Pancherz superimposition and grid analysis pre- and posttreatment. Independent sample t-test, Mann-Whitney U-test, and Pearson correlation coefficient analysis were performed. Results: Significant differences were seen between the treatment and control groups during the 12 month period. Improvement in Class II relationship in the MARA group resulted from skeletal and dentoalveolar changes. There was a 7-mm molar correction and a 4.7-mm overjet reduction. There was also an increase in the mandibular base of 3.3 mm with the lower molar and incisor coming forward 2.6 mm and 2.2 mm, respectively. No significant headgear effect was shown on the maxilla. The maxillary incisor position remained unchanged, whereas the molar distalized 1.8 mm. The anterior lower facial height had an overall increase of 2.2 mm. Conclusions: The MARA was successful in achieving a Class I molar relationship and reducing the overjet in Class II malocclusions. This was the result of both skeletal and dentoalveolar changes.