Rapid maxillary expansion is a dramatic procedure with a long history. It is sometimes called, occupies unique niche in dentofacial therapy. Maxillary expansion treatment have been used for more than century to correct maxillary transverse discrepancy. Three expansion treatment modalities are used today: rapid maxillary expansion, surgically assisted rapid maxillary expansion and Mini screw assisted rapid maxillary expansion. Since each treatment modality has advantages and disadvantages, controversy regarding use of exists. Practitioner select treatment appliances based on their personal experiences and on the patients age and malocclusion.