Introduction: Aging greatly affects the structure of the blood vessels in order to adapt to – among other things – the changes in the hemodynamic environment. Thus, we investigated rat carotid arteries from young and old rats regarding changes in their structural components. Hypothesis: That aging induces substantial changes in the morphology and components of the arterial wall. Methods: Carotid arteries were isolated from young (1 month: 1m), adult (12 months: 12m) and senescent (29 months: 29m) Wistar rats. Cryosections were taken from different age groups and immunofluorescence staining for cellular and extracellular matrix components of the vessel wall was employed to determine the structural characteristics of vessels. Measurements were divided in two groups: biomechanical and morphological measurements (measurements of intensity). All measurements and analyses were performed using the Volocity image analysis program. Results: Changes in the biomechanical characteristics of carotid arteries from young to old: wall thickness, number of nuclei per section, artery inner volume, and artery wall surface increased significantly with age (p<0.05). Changes in the intensity of extracellular matrix components of carotid arteries from young to old: smooth muscle actin, elastin, endothelium marker MECA-32, nuclei, laminin Pan, laminin γ1, laminin α2, laminin α5, laminin β2, collagen I, collagen III, collagen IV, increased significantly with age (p<0.05). The most substantial change was found in collagen type I and III, laminin γ1 and smooth muscle actin. Conclusions: The data suggest that aging results in substantial structural changes in the vascular wall. Vessels size increases with age and it is associated with increases in extracellular matrix components, especially the fibrillar collagen content (collagen type III), which is several times higher than that of the laminins which increase evenly with age. I. Ivic1, L. Yousif2, Z. Vamos1, P. Cseplo1, R. Hallmann2, L. Sorokin2, A. Koller1 1University of Pecs, Medical School, Department of Pathophysiology and Gerontology, Pecs, Hungary 2University of Münster, Institute of Physiological Chemistry and Pathobiochemistry, Münster, Germany