Objective: The purpose of this study is to examine the structural variations in aortic wall according to age, including a specific age group in the age spectrum using newborn tissue samples The distribution, density, sequences, structural characteristics, thickness and quantitative changes of the elastic fibers were examined ultrastructurally. Methods: The aorta tissue samples used in this study were taken from rats supplied from Ankara Ibni Sina Hospital. The female Wistar-albino rats were selected from five different age groups, which are- infants, 5 week, 7 week, 3 months and 1 year. The average weights of the rats were determined as 4,5-6 gr for infants, 110 g for 5 week age group, 130 g for 7 week age group, 220 g for 3 month age group and 350 g for 1 year age group. The aorta tissue samples from all age groups were prepared for electron microscopy method. The half thin sections were stained with toluidine blue for light microscopy and the tissues stained with osmium for Transmission Electron Microscope were also evaluated. Results: In the investigations with light microscopy and TEM, the internal elastic lamina was thickened for a while and in older ages it became thinner. We observed that pinocytotic vesicles of young rats in both the basal and apical cell membrane were almost equal and in older rats the vesicles on apical surface were concentrated and the endothelial cells became irregular. Depending on age, the proliferation of smooth muscle cells increased, and significant increase of smooth cells were found in internal elastic lamina. Conclusion: Aging is a very complex process, in which it is observed that intima and elastic lamels in aorta become thinner, the connective tissue and muscle cells increase between elastic fibers, distortion and degeneration occur in some places in endothelial cells and the activities of organelles and organs decelerate or distort. In conclusion, it was determined that aorta was degenerated by aging. ©Copyright 2011 by Gazi University Medical Faculty.