is a treatment method used in maxillary deficiencies, nasal airway insufficiencies, severe cross-bites, Class III cases in which surgical intervention is not needed and cleft lip and palate patients. An orthopedic change is obtained through the separation of midpalatal suture by this appliance. It is known that R.P.E. can be applied to adults as well as young patients considering the limitations of stability and expansion amount by age. In this report an application of R.P.E: on a 18 year old female Class III patient is presented with treatment results. After a 18 day palatal expansion the appliance was held in the mouth for 3 more months then a fixed appliance treatment was started. Correction of Class III malocclusion was obtained at the end of a 13 month treatment.

Keywords: Rapid Palatal Expansion, Class III, Adult