The anatomy of the glenohumeral joint in humans is characterized by static and dynamic stabilizing structures. In particular the glenoid labrum (GL), the proximal attachment of the joint capsule and the lateral glenohumeral ligament, is an important passive stabilizer in the human shoulder. Although canine animal models are used frequently to investigate the complex biomechanics of the shoulder, few data regarding the microstructure of the canine GL are available. In this study, the anatomy of the canine GL and related structures (n = 20) was investigated and compared with the human anatomic situation (n = 36). In both human and beagle joints, the GL consisted of 3 zones-the transition zone, shifting zone, and meniscoid fold, but not all 3 zones were present in all joint segments from canine joints. In particular the peripheral parts of the GL showed rich vascularization in both species. The height and width of the GL in the histologic specimens indicated that the GL is of less importance as a passive stabilizer in dogs. Additional differences between the human and canine CL include the joint ligaments, tendons of the shoulder joint, and lack of rotator cuff. The structural and biomechanical characteristics of the joints of quadrupedal animals raise the question of their appropriateness for shoulder research.