We operatively treated, between 1978 and 1987, twenty-one shoulders in nineteen patients, fifty-four to eighty-four years old, who had disabling pain attributable to a massive tear of the rotator cuff, accompanied by loss of the surface of the glenohumeral joint. These patients were not candidates for total shoulder replacement because of the massive deficiency in the cuff and the fixed upward displacement of the humeral head. A prerequisite for hemiarthroplasty was a functionally intact coracoacromial arch to provide superior secondary stability for the prosthesis. One important aspect of the operative technique was the selection of a sufficiently small prosthesis so that excessive tightness of the posterior aspect of the capsule could be avoided. Eighteen shoulders in sixteen patients were available for follow-up, which ranged from twenty-five to 122 months. Pain decreased from marked or disabling in fourteen shoulders preoperatively to none or slight in ten and to pain only after unusual activity in four. Active forward elevation improved from an average of 66 degrees preoperatively to an average of 109 degrees postoperatively. One patient, who had had an excellent result, fell and sustained an acromial fracture, so the functional result changed to poor. Three patients had persistent, substantial pain in the shoulder that led to a revision. Neither infection nor prosthetic loosening developed in any shoulder.