Study of the morphological pattern of the arteries in the rotator cuff does not produce any evidence that the "critical zone" for ruptures and calcified deposits is much less vascularised than any other part of the tendinous cuff. This work, however, does show conclusively that the "critical zone" of the rotator cuff corresponds to the zone of the anastomoses between the osseous and tendinous vessels. Age does not seem to have a decisive influence on the morphology of the vascular pattern.