A schema of treatment of the three types of acromioclavicular injuries, based [See table in the PDF file] on pathological change in each, is presented. Type-I injuries are those with direct trauma to the acromioclavicular joint without significant ligamentous tears or intability. Type-II injuries are those with acromioclavicular ligamentous injury and instability but without disruption of the coracoclavicular ligaments. Type-III injuries are those with complete clavicular instability and disruption of both sets of ligaments. Type-I injuries are treated expectantly when seen early, and when seen late, with acromioclavicular arthritis, they are treated by resection arthroplasty. Expectant treatment is advocated for early Type-II injuries while late symptomatic Type-II separations are treated by resection arthroplasty of the acromioclavicular joint. Those patients with acute and chronic Type-III injuries are treated surgically by a new operation which combines resection arthroplasty of the acromioclavicular joint with fixation of the clavicle in an anatomical position by suture of the acromial end of the shortened coraco-acromial ligaments into the medullary canal of the clavicle. The results in both acute and chronic cases, fifteen in number, have been quite good.