With our limited access to the literature we have been unable to find any satisfactory description for an arthroplasty of the shoulder-joint. Having a case for operation, we began the work on the cadaver and developed the following technic, which we believe is nearest anatomically correct of anything we have been able to find. In this operation we have utilized a portion of the short head of the biceps for a flap to interpose, because it is covered bymore dense tendinous sheath than any other structure in the neighborhood of the shoulder-joint, is correctly located anatomically and we believe in the majority of cases will furnish sufficient fascia and muscle to make a flap of necessary dimensions. The flap obtained is quite sufficient to line the glenoid fossa and cover the entire head of the humerus. In our clinical case there was considerable enlargement of the head of the humerus,