We report a prospective study of 46 patients with acute complete dislocation of the acromioclavicular joint. They were all treated by suture of the deltoid and trapezius over the clavicle with no repair of the coracoclavicular ligaments, using only temporary fixation with two wires. At operation 43 patients (93.5%) had damage to the trapezius or deltoid or both. The coracoclavicular ligaments were intact in six (13%). Follow-up was from 2 to 7.9 years (mean 5.8), and at the latest review only five patients (10.9%) had redisplacement, due to premature removal of wires for infection in one, to migration of the wires in another and to partial failure of the muscle repair in three. We consider that the deltoid and trapezius attachments are important clinical stabilizers of the clavicle and that their repair, with reinforcement, is a useful addition to any method of surgical treatment.