The Acromioclavicular joint is classified as a diarthrodial joint. Its stability is maintained by articular capsule, acromioclavicular ligament, articular disc, coraco clavicularligament(trapezoid and conoid ligament) and attached muscles. 17 cases of acromioclavicular dislocation which had been seen at Seoul Red Cross Hospital during the period of January 1975 through December 1977 were studied. The following observations were made. 1. This injury is more prevalent in male (82%) with the peak incidence in the 3rd and 4 th decades (53%). 2. Conservative treatment was given in 11 cases by adhersive strapping around the elbow and lateral one third of the clavicle reinforced by Velpeau dressing for 3 weeks, then followed by active exercise. 3. Operative treatment consist of modified Phemister technique in 3 cases, Mumford technique in 2 cases, and Dewar and Barington's technique in 1 case. 4. Results were evaluated in 4 groups as excellent, good, fair, and poor according to Gerald weitzman's classification(1975). 5. Overall results of more than good (satisfactory) was obtained in 72.7% of the 11 cases with conservative treatment and in 50% of the 6 cases with operative treatment.