Osteolysis of the distal part of the clavicle was diagnosed in forty-six men, none of whom had a history of acute injury to the acromioclavicular area. All patients were athletes and forty-five lifted weights as part of their training. Pain and tenderness at the acromioclavicular joint associated with radiographic signs of osteoporosis, loss of subchondral bone detail, and cystic changes in the distal part of the clavicle were present in varying degrees. Joint scintigraphy showed increased activity in the distal part of the clavicle in all patients. Resection of the distal end of the clavicle in twenty-one patients, four with bilateral procedures, resulted in relief of symptoms in the nineteen who were followed. All but five of these patients were able to continue their sports activities and weight-training. The twenty-five patients who were not operated on also had improvement, but only after cessation or change of their sports activity and avoidance of weight-training.