Arthroscopic subacromial decompression and rotator cuff debridement was performed on 61 consecutive patients with either stage II or stage III impingement syndrome: 27 with no actual tear of the cuff (group IIa); 21 with a partial-thickness tear (group IIb); and 13 with full-thickness tears (group III). Patients were seen in follow-up at a minimum of 2 years (mean 27.7 months). Apical oblique and outlet radiographic views of the shoulder were used to evaluate both preoperative subacromial pathology and to document removal of adequate bone postoperatively. Patients were evaluated pre- and postoperatively using both the UCLA Shoulder Rating Scale and Neer's criteria: Twenty-four of the 61 cases were compensation related. Mean motion improved postoperatively for all stages of impingement. For all patients, preoperative UCLA and Neer ratings were unsatisfactory. In group IIa, postoperative UCLA and Neer ratings improved in 22 patients to an 81% satisfactory result rate. In group IIb, 17 patients had major improvement in UCLA and Neer ratings (also an 81% satisfactory result rate). In group III, there were 10 satisfactory and three unsatisfactory results for a 77% satisfactory result rate. Of the 10 satisfactory results, eight were in patients who were either retired or worked at sedentary jobs that did not demand above-shoulder activities and strength, and whose principal preoperative complaint was pain. All 10 of these patients had relief of their pain; the three unsatisfactory results were all compensation cases in manual laborers, one later having a satisfactory result from an open cuff repair.(ABSTRACT TRUNCATED AT 250 WORDS)