Fifteen unilateral crossbite patients of primary and mixed dentition with mandibular asymmetry were treated by transverse expansion using removable appliance. Posteroanterior cephalometric analysis was utilized before and after treatment. The results suggested that after the correction of unilateral crossbite, the deviation of midsagittal mandibular total lenth decreased significantly. According to this study, early treatment of unilateral crossbite is indicated.