A 15-month follow-up study was conducted on 13 children with unilateral cleft lip and palate. The patients presented with short upper lip, abnormal lip seal, and maxillary retrusion. All had undergone surgery in childhood. Cephalometric and electromyographic measurements were made prior to the start of treatment, 4 months into treatment, and after 15 months of continuous wear of a special removable appliance. The cephalometric measurements on paired comparison showed major improvement in both the sagittal maxillary and dentoalveolar positions. The electromyographic activity of the superior orbicularis oris muscle demonstrated no significant changes over the treatment period. Improvement in the sagittal maxillary and dentoalveolar positions seems to suggest that the elimination of the restrictive effect of the superior orbicularis oris muscle is a good therapeutic approach to promote normal growth potential in children with cleft lip and palate.