Arthroscopic subacromial decompression was performed on 114 patients with rotator cuff impingement who had not responded to nonoperative measures. None of the patients had a full-thickness cuff tear. Patients with associated instability, symptomatic acromioclavicular joint disease, or ruptures of the long head of biceps were not included. Results were determined by questioning patients about their satisfaction with the outcome of surgery and by functional assessment of the shoulder with the parameters of pain, ability to perform daily activities, and range of motion according to the Constant scoring system. When reviewed at a mean interval of 19 months after surgery, 85 patients (75%) were satisfied with the outcome. Pain scores improved by an average of 8.6 points; "activities of daily living" scores improved by an average of 5.8 points; range-of-motion scores improved by an average of 3.6 points. The improvements in all 3 parameters scored were significant (P < .05). The following variables were statistically analyzed to assess their influence on final outcome: age, sex, occupation, duration of symptoms before surgery, dominance of the affected shoulder, outcome of the impingement test, state of the cuff, and experience of the surgeon performing the operation. The duration of symptoms before surgery was the most significant predictor of outcome. Symptoms of prolonged duration were associated with an unsatisfactory subjective results (P < .01) and with smaller improvements in the parameters of the Constant score (P < .001). Recovery after arthroscopic subacromial decompression and eventual outcome were related to the extent of cuff damage. Patients with partial thickness tears or fraying of the cuff had a delayed return to work (P < .001) and were found to have smaller increases in the pain and range-of-motion scores (P < .05). A satisfactory subjective result was most often associated with a positive impingement test (P < .05). Unsatisfactory outcomes were associated with a questionable diagnosis and lack of clear evidence of impingement at arthroscopy, inadequate decompression of the subacromial space, or the presence of calcium deposits in the rotator cuff.