OBJECTIVE: To study long-term changes in the mandibular asymmetry of patients with hemimandibular elongation (HE) treated with two-phase surgical orthodontic approach. DESIGN: Descriptive clinical study. SETTING AND SAMPLE POPULATION: Private practice setting. Seven (six females) out of 47 diagnosed and treated patients for severe mandibular asymmetry were included with the following criteria: diagnosis of HE based on clinical, radiological and single photon emission computed tomography bone scintigraphic studies, good quality orthopantomograms (OPT) available at six time-points, two-phase surgical treatment (high condylectomy, HC, and orthognathic surgery, OS) and measurements of maximal mouth opening (MMO) available. METHOD: Mandibular ramus height and corpus length were measured on OPTs at six time-points. Ratios between the affected/non-affected sides were calculated. RESULTS: All patients had progression of mandibular asymmetry before any operation, which finding together with the scintigraphy resulted to the decision to perform HC. Thereafter ramus and corpus asymmetry decreased compared with the initial measurements. After OS, stable symmetry of corpuses and alignment of skeletal and dental midlines were obtained. MMO reduced on average 50% after HC, regained 20% after OS and recovered almost totally at the last follow-up. CONCLUSIONS: High condylectomy to stop excessive growth and OS to correct facial asymmetry is considered successful and necessary treatment for patients with HE. MMO can well recover after surgical traumas. Orthodontists should consider mandibular asymmetry as abnormal and need for surgical treatment if asymmetry is progressive and the ratio between affected/non-affected sides approaches 10%.