Cephalometric measurements and electromyographic analysis of the superior orbicularis oris muscle were undertaken in 13 children with unilateral cleft lip and palate with a short upper lip length who have undergone surgery in childhood. Initially, cephalometric and electromyographic records were evaluated and again after the subjects had continuously worn, for 4 months, a removable appliance specially designed to avoid the restraining effect of superior orbicularis oris muscle activity over the maxilla. Comparison between pretreatment and posttreatment cephalometric measurements showed a significant improvement in both the sagittal position of the maxilla and the dentoalveolar position. No significant changes were observed in electromyographic activity during rest or when saliva swallowing. Cephalometric changes suggest that the removable appliance used improves the growth of the maxilla.