Fixed functional appliances have dramatically altered the therapeutic armamentarium for Class II malocclusions, and orthodontists have enthusiastically endorsed them. The newest of these appliances, and perhaps the least appreciated, is the mandibular anterior repositioning appliance. The mandibular anterior repositioning appliance does not connect the mandible and maxilla through pistons, wires, springs, coils, or other mechanisms, as do other Class II appliances. Orthodontic clinicians have considered these appliances as exclusively adolescent Class II therapies, but recent experience has shown that they can effect favorable changes in adults as well. The mandibular anterior repositioning appliance offers orthodontists and their patients an effective alternative to some of the traditional therapies for Class II malocclusions. World J Orthod 2003;4:135–144.