The aim of this study was to determine the effects of a magnetic appliance in functional Class III patients. Standardized lateral head cephalograms and hand-wrist films of 10 subjects (mean age nine years seven months) were taken. These records were repeated after a period of one year, and the serial films were compared to determine the direction of facial growth as the control group. After this observation period, the magnetic appliance was placed in the 10 patients for approximately 9.4 months. The significant findings showed a posterior rotation of the mandible (x = 2.1 +/- 0.7 degrees), increased overjet (x = 4.8 +/- 0.3 mm), decreased overbite (x = -3.7 +/- 0.7 mm), protrusion of the upper incisors (x = 6.2 +/- 1.2 degrees), retrusion in the lower incisors (x = -0.6 +/- 0.3 degrees), reduced SNB angle (x = -1.8 +/- 0.8 degrees), increased ANB angle (x = 1.9 +/- 0.3 degrees), and an increased mandibular plane angle (x = 2.1 +/- 0.7 degrees). The results of this study indicate that the primary effect of magnetic appliance was the increase in the posterior rotation of the mandible.