The purpose of this study was to determine whether asymmetries in the transverse dimension are corrected after orthodontic treatment and to determine differences between age-group responses in the correction of transverse asymmetries. Sixty orthodontically treated subjects with transverse asymmetries in arch width were grouped by age, treatment modality, and arch location. Casts were analyzed to assess the correction of arch asymmetry. Lateral cephalometric analysis was performed to assess vertical change differences between age groups, and to detect correlations between vertical and arch-width changes. After orthodontic treatment, it was found that the arch width between the 2 halves of the arch still showed significant differences (P < .05); it was also found that arch-width changes between pretreatment and posttreatment showed significant differences (P < .05) for nonextraction treatment and for the anterior region in extraction treatment. Analysis of lateral cephalograms showed significant differences (P < .05) in vertical-dimension changes between growing and nongrowing subjects. The Pearson product moment correlation test showed no significant correlation at the P < .05 level between vertical and arch-width changes. We concluded that, for this sample, asymmetry in transverse dimension was not corrected, and there was no difference between growing and nongrowing individual responses in transverse asymmetry correction.