BACKGROUND Age at injury is believed to be a factor that strongly influences functional outcome after nerve injury. However, there have been few long-term evaluations of the results of nerve repair and reconstruction in children. Our aim was to evaluate the long-term functional outcome of nerve repair or reconstruction at the forearm level in patients with a complete median and/or ulnar nerve injury at a young age. METHODS Forty-five patients were assessed at a median of thirty-one years after a complete median and/or ulnar nerve injury in the forearm. The outcome was classified with a total score (the Rosén score), a standardized outcome instrument consisting of three separate domains for sensory and motor function as well as pain/discomfort. In addition, the DASH (Disabilities of the Arm, Shoulder and Hand) score, sensitivity to cold, and locognosia were assessed specifically, together with the patient's estimation of the overall outcome and impact on his or her education, work, and leisure activities. Comparisons were made between injuries that occurred in childhood (less than twelve years of age) and those that were sustained in adolescence (twelve to twenty years of age), and according to the nerve(s) that was injured (median nerve, ulnar nerve, or both). RESULTS Functional recovery, expressed as the total outcome score, the sensory domain of that score, and the patient's subjective estimation of outcome, was significantly better after injuries sustained in childhood than after those that occurred in adolescence (87% and 67% of complete recovery, respectively; p < 0.001). No significant differences in recovery were seen between median and ulnar nerve injuries, or even when both nerves were injured. Motor function was close to normal, and cold sensitivity was not a problem in either age group. The median DASH scores were within normal limits and did not differ between the groups. Patients who sustained the injury in adolescence indicated that the nerve injury had a significantly higher effect on their profession, education, and leisure activities. CONCLUSIONS At a median of thirty-one years after a median or ulnar nerve repair at the level of the forearm, nerve function is significantly better in those injured in childhood than in those injured in adolescence, with almost full sensory and motor recovery in individuals injured in childhood.