Sixteen patients underwent hemiarthroplasty for rotator cuff arthropathy between June 1989 and March 1992, and evaluations obtained before and after surgery in all patients were compared. A modular head large enough to articulate with the coracoacromial arch but not so large as to prevent approximately 50% of humeral head translation on the glenoid was used in these cases. Each patient was evaluated with Neer's limited goals rating scale after an average follow-up of 33 months (24 to 55 months). Ten patients were rated as successful and six as unsuccessful. Four of the six unsuccessful patients had undergone at least one attempt at rotator cuff repair with acromioplasty before the index procedure, and two of these four patients had deficient deltoid function after this rotator cuff surgery as a result of postoperative deltoid detachment. Also, three of these four patients who had previously undergone acromioplasty subsequently had anterosuperior subluxation after hemiarthroplasty. Hemiarthroplasty did not provide for a successful outcome in all patients with rotator cuff arthropathy. However, 10 of the 12 patients in this series with good deltoid function and an adequate coracoacromial arch were rated as successful by Neer's limited goals criteria. In addition, this study illustrates that formal acromioplasty carried out during attempts at rotator cuff repair in such patients may jeopardize the subsequent success of hemiarthroplasty.