Arthroscopic acromioplasty has become a common procedure for the treatment of chronic impingement syndrome. Short-term studies have consistently shown good results; however, long-term data have not previously been reported in the literature. Of 102 consecutive patients undergoing arthroscopic acromioplasty at our institution from 1984 to 1988, 82 patients (83 shoulders) were available for evaluation. The patients were reviewed after a mean of 8 years, 5 months from their original surgery. There were 16 failures (19%) with unsatisfactory results following surgery; 13 patients (15%) required further surgery to relieve persistent pain. Thirty-three percent of all patients previously involved in sports were unable to return to overhead and throwing sports due to pain and lack of power with throwing. Overall, 81% of patients in our series had good to excellent results after 6 to 10 years. To optimize the indications for the procedure, other causes of impingement, such as occult instability and degenerative joint disease, should be ruled out. Throwers may have difficulty returning to their sport at the same level of intensity, and should be addressed independently.