BACKGROUND and OBJECTIVES: Aging exerts a number of deleterious changes in the cardiovascular system, and, in particular, on the large arteries. Previous studies have suggested that augmentation index (Aix) and aortic pulse wave velocity (aPWV) increase linearly with age, yet epidemiological data concerning arterial stiffness suggest that large artery stiffening predominantly occurs later in life. Therefore, the aim of the study was to test the hypothesis; 1) age-related changes in AIx are more prominent in younger individuals, whereas changes in aortic stiffness per se are more marked in older individuals, 2) whether these changes are similar between Caucasians and Koreans. METHODS 1,188 subjects aged 17 to 87 years (mean age of 45.5 years and female 52%) were included and all were apparently healthy and free of any medication for hypertension, diabetes and dyslipidemia. Aix and aPWV were measured by pp-1000 and Gaon 21 (both Hanbyul Medtech, Korea). RESULTS Women showed significantly higher central Aix (15.4 vs. 22.5 of men, p<0.001) even with lower peripheral pressure (117/72 vs. 126/78mmHg) of men, both p<0.001), but there was no difference in aPWV between sexes. Peripheral and central AIx, and aortic PWV all increased significantly with age; however, the age-related changes in AIx (r=0.333, p<0.001) and aortic PWV(r=0.194, p<0.001) were non-linear, with AIx increasing more in younger individuals, whereas the changes in PWV were more prominent in older individuals, which were similar to the changes in Caucasians (The Anglo-Cardiff Collaborative Trial (ACCT). CONCLUSIONS These data suggest that 1) there is sex-difference in Aix according to aging, 2) AIx might be a more sensitive marker of arterial stiffening and risk in younger individuals but aortic PWV is likely to be a better measure in older individuals.