From September 1974 to December 1987, seventy-one patients were operated on for valgus instability of the elbow. The average length of follow-up of sixty-eight patients (seventy operations) was 6.3 years (range, two to fifteen years). At the operation, a torn or incompetent ulnar collateral ligament was found. Fourteen patients had a direct repair of the ligament, and fifty-six had a reconstruction of the ligament using a free tendon graft. The result was excellent or good in ten patients in the repair group and in forty-five (80 per cent) in the reconstruction group. Seven of the fourteen patients who had a direct repair returned to the previous level of participation in their sport. Of the fifty-six who had a reconstruction, thirty-eight (68 per cent) returned to the previous level of participation. Twelve of the sixteen major-league baseball players who had a reconstruction as the primary operation (no previous operation on the elbow) were able to return to playing major-league baseball, and two of the seven major-league players who had a direct repair returned to playing major-league baseball. Previous operations on the elbow decreased the chance of returning to the previous level of sports participation (p = 0.04). Fifteen patients had postoperative ulnar neuropathy. This was transient in six patients, only one of whom was unable to return to the previous level of sport. The other nine patients had an additional operation for the neuropathy; four were able to return to the previous level of sport.