Difficulties that occur during limb lengthening were subclassified into problems, obstacles, and complications. Problems represented difficulties that required no operative intervention to resolve, while obstacles represented difficulties that required an operative intervention. All intraoperative injuries were considered true complications, and all problems during limb lengthening that were not resolved before the end of treatment were considered true complications. The difficulties that occurred during limb lengthening include muscle contractures, joint luxation, axial deviation, neurologic injury, vascular injury, premature consolidation, delayed consolidation, nonunion, pin site problems, and hardware failure. Late complications are those of loss of length, late bowing, and refracture. Joint stiffness may also be a permanent residual complication. Pain and difficulty sleeping are other problems that arise during limb lengthening, especially in the more extensive cases. Forty-six patients had 60 limb segments lengthened between 1.0 and 16.0 cm, with a mean of 5.6 cm. The average treatment time was approximately one month per centimeter for single-level lengthenings with no deformity and 1.2 months per centimeter with deformity correction. The lengthening index for double-level lengthening was 0.57 month per centimeter with no deformity and 0.90 month per centimeter with correction of deformity. In adults, the lengthening index was 1.7 months per centimeter for single-level and 1.1 months per centimeter for double-level lengthening. There were 35 problems that had to be resolved in the outpatient clinic. There were 11 obstacles that required additional operative intervention to resolve. There were 27 true complications, of which 17 were considered minor and ten were considered major complications. Of the major complications, three interfered with achieving the original goals of treatment. All three required further operative intervention to achieve the original goal. These were nonunion in one and late bowing in two. Despite these problems, obstacles, and complications, the original goals of surgery were achieved in 57 of the 60 limb segments treated. Patient satisfaction was achieved in 94% of 46 cases.