Between 1974 and 1990 a Neer humeral hemiarthroplasty was used in 20 patients (21 shoulders) with combined glenohumeral arthritis and complete degenerative lesions of the rotator cuff. Patients were monitored for an average of 4 years (range 2 to 6.6 years). The coracoacromial ligament was preserved as a restraint against anterosuperior displacement. The rotator cuff defect was irreparable, and no attempt was made to cover the superior defect. Two patients underwent transfer of the sternocostal portion of the pectoralis major to the lesser tuberosity for subscapularis insufficiency and anterior subluxation. After the operation rehabilitation of the deltoid was aggressively pursued. With limited goals criteria described by Neer, 18 (86%) shoulders achieved satisfactory results. Pain scores improved from a mean of 2.9 (scale of 0 to 3) before operation to 0.6 after operation. All patients had lower pain scores after operation. However, only 12 shoulders had no pain (pain score of 0). Average active flexion improved to 120 degrees after operation from 70 degrees before operation. However, five patients achieved less than 90 degrees of active flexion after operation. Active external rotation improved from a mean of 27 degrees (range 0 degrees to 65 degrees) to a mean of 46 degrees (range 0 degrees to 70 degrees). No instances of postoperative instability occurred. Although the results of hemiprosthetic replacement in this difficult patient population are inferior to results experienced by patients with an intact rotator cuff, the improvement of pain and preservation of function obtained make it an attractive alternative to arthrodesis, resection arthroplasty, or constrained arthroplasty.