The isolated fracture of the ulnar shaft is notorious for prolonged healing time. Over a twenty-seven-month period, seventy-one such fractures were treated at our institution. The initial twelve fractures were immobilized with the standard axilla-to-palm plaster cast. They had an average healing time of 10.5 weeks and a non-union rate of 8 per cent. The remaining fifty-nine fractures were treated without a cast or with a cast or splint for no longer than two weeks after injury and then mobilization as tolerated. In this group the average healing time was 6.7 weeks and there were no non-unions. The motion at the wrist and elbow was always regained, and the average loss of forearm rotation was 5 degrees.