The object of this paper is to report on the findings of a retrospective study of 40 patients with 41 shoulders with persistent painful arc syndrome secondary to a chronic coracoacromial ligament inflammation who underwent simple coracoacromial ligament division at the Toronto East General and Orthopaedic Hospital between January 1973 and June 1979. Initial therapy was always nonoperative. Surgical intervention was reserved for patients who did not respond to conservative management and who had a painful arc with tenderness of the coracoacromial ligament. The aim of the coracoacromial ligament division was to relieve impingement by releasing the coracoacromial arch. Patients were carefully examined to rule out associated neck pathology, rotator cuff problems, and lesions of the acromioclavicular joint. Any patients with significantly large osteophytes under the anterior acromion were excluded. Forty patients (41 shoulders) were questioned and examined in followup. There were 29 males and 11 females. The ages ranged from 21 to 72 years (average 43.5 years). In 21 shoulders (51%), there was a history of trauma as the initiating factor. The follow-up ranged from 8 to 76 months (average 36.3 months). According to a described rating system, the results were satisfactory to excellent in 39 of 41 shoulders (95%) and unsatisfactory in two of 41 shoulders (5%). The back to work time ranged from 1 to 16 weeks (average 5.7 weeks).(ABSTRACT TRUNCATED AT 250 WORDS)