The aim of this study was a better understanding of the role of the vascular supply as a pathogenic factor in rotator cuff disease. Twenty-five shoulders from unembalmed cadavers were studied after injection of the upper limb aa. with barium sulfate. The predominant arteries were the vessels of the subscapularis m. These branches originated from the axillary a. the anterior circumflex humeral a., and the posterior circumflex humeral a. The supraspinatus m. was supplied by the suprascapular a. but the acromial branch of the thoracoacromial a. supplied the tendon of the supraspinatus. The infraspinatus and teres minor tendons were vascularised by the ascending branches of the posterior circumflex humeral a. The tendon of the long head of the biceps brachii m. was supplied by a branch termed the "arcuate artery" and by a branch we describe derived from the brachial a. at the level of the latissimus dorsi tendon and travelling in a true mesotendon. There is a very real critical zone, with a lesser blood-flow, 1.5 cm from greater tubercle, situated mainly at the supraspinatus tendon. This is a convergence zone of the anterior and posterior circumflex humeral aa., the suprahumeral a. and the thoracoacromial a. The histologic studies confirmed the poor vascularity of this critical zone.