Objective: To inrestigate the changes of elastin and elastic fibers in the tunica media of the ascending aorta in patients with Stanford type A aortic dissection (AD). Methods: Ten specimens of dissected ascending aortic wall tissue obtained from patients with Stanford type A AD during surgery, and 10 specimens of normal ascending aortic wall tissue taken from brain-dead donors during organ donation surgery or patients undergoing coronary artery bypass grafting were collected. In the tunica media of the two groups of specimens, the elastin expressions were determined by Western blot, and the morphological features and contents of elastic fibers were analyzed by EVG staining.Results: Results of Western blot showed that the elastin level in the tunica media of the dissected ascending aorta was significantly lower than that in the tunica media of the normal ascending aorta [(0.32±0.07) vs. (1.12±0.17), t=6.722, P=0.003]. Results of EVG staining demonstrated that the morphology and arrangement of the elastic fibers in the tunica media of dissected ascending aorta were disordered with elastic lamina fracture and loss in dissected ascending aorta, while the elastic fibers were densely and orderly arranged with integrated structure and distinct gradations of the elastic lamina; the content of elastic fibers in tunica media of the dissected ascending aorta was significantly lower than that in tunica media of the normal ascending aorta [(85 762.8±106.2) vs. (164 482.8±161.4), t=5.902, P<0.001]. The elastin and elastic fiber contents were positively correlated in tunica media of both dissected and normal ascending aortas (r=0.953, 0.973, both P<0.001). Conclusion: The contents of elastin and elastic fibers are reduced and the morphology and arrangement of the elastic fibers are disordered in the tunica media of ascending aorta in patients with Stanford A type AD, and these changes may play an important role in the pathogenesis of AD.