The effectiveness of arthroscopic surgery, supervised exercises, and placebo was compared in 125 patients with rotator cuff disease (impingement syndrome stage II) in a randomized clinical trial. The median age was 48 years, and the median duration of complications was 1 to 2 years. The treatments were arthroscopic subacromial decompression performed by 2 experienced surgeons, an exercise regimen supervised for 3 to 6 months by 1 experienced physiotherapist, or 12 sessions of detuned soft laser (placebo) for 6 weeks. The criterion for success was a Neer shoulder score > 80. Fifteen (50%) and 11 (22%) of the patients randomized to placebo and exercises, respectively, had surgery during the 2 1/2-year follow-up period and were classified as having failure with the treatments. The success rate was higher (P < .01) for patients randomized to surgery (26 of 38) and exercises (27 of 44) compared with the placebo group (7 of 28). The odds ratio for success after surgery compared with exercises was 1.5 (95% confidence interval 0.6 to 3.7; P = .49). Including all patients who underwent operation, the success rate in those not on sick leave (19 of 21) before surgery was higher compared with those on sick leave (18 of 36) (adjusted odds ratio 5.6 [1.2 to 29.2]). Similar results were observed for patients not receiving versus those receiving regular pain medication before surgery (adjusted odds ratio 4.2 [1.2 to 15.8]).