For the release of mechanical impingement occurring during the movement of the humeral head and its overlying rotator cuff beneath the coracoacromial arch, 21 patients who had a painful arc resistant to conservative treatment, were treated by subacromial recession operations. The procedure consisted of resection of the coracroacromial ligament, anterior acromioplasty, excision of the acromioclavicular joint and shaving of the greater tuberosity. Resection of the coracoacromial ligament was carried out in all patients. The other procedures were added when required for complete release of the impingement. Nineteen patients obtained satisfactory results with a minimum follow-up of one year. A satisfactory result was obtained only when the operative procedure relieved the specific mechanical impingement, i.e., coracoacromial ligament, acromial spur, osteoarthritic acromioclavicular joint or exuberant greater tuberosity.