A modified Neer acromioplasty, subacromial decompression, and debridement of massive, irreparable lesions of the supraspinatus and infraspinatus tendons was performed in fifty-seven patients. Fifty patients (fifty-three shoulders) were followed for an average of six and one-half years. The average age of the patients was sixty years (range, thirty-eight to seventy-four years). The results, as rated on the basis of pain, function, range of motion, strength, and satisfaction of the patient, were satisfactory in forty-four shoulders (83 per cent) and unsatisfactory in nine (17 per cent). A favorable outcome was observed in shoulders in which both the anterior portion of the deltoid muscle and the long head of the biceps tendon were intact and in which a previous acromioplasties or operations on the rotator cuff had been performed. An unsatisfactory outcome was observed in shoulders in which the anterior part of the deltoid muscle was weak or absent or in which a previous acromioplasty and attempted repair of the rotator cuff had been performed. The active forward flexion of the shoulder improved from an average of 105 degrees preoperatively to an average of 140 degrees postoperatively. The results of the present study suggest that, with proper rehabilitation, adequate decompression of the subacromial space, anterior acromioplasty, and debridement of massive tears of the rotator cuff can lead to the relief of pain and the restoration of shoulder function.