The purpose of this study was to evaluate the skeletal and dental effects produced by the Fränkel functional regulator III appliance in growing children with Class III malocclusions. Thirty preadolescents (initial mean age, 8.0 +/- 1.2 years; mean treatment duration, 1.3 +/- 0.6 years) treated with the Fränkel functional regulator III appliance were compared with 20 matched untreated Class III controls (initial mean age 8.2 +/- 1.1 years; mean observation period, 1.5 +/- 0.6 years). The treatment effects were mainly from backward and downward rotation of the mandible and linguoversion of the mandibular incisors.