The purpose of this study was to examine the nature and number of complications relative to magnitude of limb lengthening. Results and complications of 50 limb-lengthening procedures were analyzed. There were 49 patients. Mean age was 21 years (range, 7-48 years). Lengthening was performed in 24 femora, 18 tibiae, 4 humerii, 3 radii, and 1 ulna. Average length gained was 5 cm (range, 3-15 cm) at average follow-up of 48 months (range, 12-76 months). Desired length was accomplished in all but 1 patient. The 69 complications varied in severity, but only 5 of these significantly impaired end results. The most serious complications occurred in patients with >30% bone lengthening. Patients with <15% lengthening had a significantly decreased complication rate. The healing index was lower in children. We conclude that incidence and severity of complications after limb-lengthening procedures are significantly influenced by relative lengthening of bone.