The authors report a prospective five-year follow-up study of 52 patients who had arthroscopic subacromial decompression for advanced (stage II: type 1 and 2) rotator cuff disease. All patients were assessed preoperatively, at six months and at five years postoperatively using the Constant-Murley score and the revised American Shoulder and Elbow Surgeons (ASES) score. From six months until five years postoperatively, 45 (out of 52) patients showed a further progressing improvement and relief of symptoms. This is established by a significant (p < 0.001) increase of the mean Constant-Murley score from 76.4 at six months postoperatively to 84.9 at five years postoperatively.