Eight patients (average age, 10 years) had a unilateral forearm lengthening procedure using the technique developed by Ilizarov. The procedure was performed in 4 patients with radial agenesis, in 2 with multiple hereditary exostosis, in 1 with ulnar agenesis, and in 1 with multiple enchondromatosis. Patients underwent distraction osteogenesis through either a unifocal or bifocal corticotomy. Forearm length increased on average 6.0 cm (range, 3.6-8.1 cm) or 54% (range, 21% to 94%) with a lengthening index of 1.3 months per centimeter (range, 0.6-1.9 months per centimeter). The length of follow-up averaged 4.5 years and involved office examinations with task evaluation and a questionnaire addressing function and appearance. Limb length discrepancy at follow-up measured 3.7 cm (range, 0.0-8.0 cm). Lengthening of the forearm was found to improve upper extremity function; it allowed the patient to reach distant body parts and to perform select activities requiring near-equal arm length. Forearm lengthening also improved the appearance of the arm if adequate soft tissue was preserved. Full restoration of arm length was not a requirement for a successful outcome and patient satisfaction with the results of the procedure was high.