Reconstruction of the ulnar collateral ligament using a free tendon graft was performed on sixteen athletes. All participated in sports that involved throwing (mostly professional baseball), and all had valgus instability of the elbow. After reconstruction and rehabilitation, ten of the sixteen patients returned to their previous level of participation in sports, one returned to a lower level of participation, and five retired from professional athletics. Despite precautions, there was a high incidence of complications related to the ulnar nerve. Two patients had postoperative ulnar neuropathy (one late and one early) that required a secondary operation, but they eventually recovered completely. Three others reported some transient postoperative hypoesthesia along the ulnar aspect of the forearm that resolved after a few weeks or months.