OBJECTIVES This study aimed to investigate the age-related changes in aortic annulus in healthy subjects and compare with findings in mitral annulus by transthoracic real-time three-dimensional(3D) echocardiography. BACKGROUND The age is the most important clinical determinant of valvular regurgitation. Valvular regurgitation in elderly population can be frequently observed especially in aortic valve. METHODS Real-time 3D echocardiography was performed in 74 healthy subjects(16 subjects under 20 years old and 58 over 20 years old). We used a novel software system with 3D echocardiography to reconstruct aortic valve in early diastole and mitral valve in midsystole. Then, the annular areas and circumferences of each valve were calculated. The relations of aortic and mitral annular size to age were studied with a linear regression analysis. RESULTS The annular areas and circumferences in aortic valve(r=0.883, p<0.001, r=0.882, p<0.001) and mitral valve(r=0.758, p=0.001, r=0.754, p=0.001) increased with age until maturity was reached. After 20 years old, the annulus area and circumference of aortic valve per body square meter(r=0.551, p<0.001, r=0.648, p<0.001) were increased gradually with aging but, those of mitral valve weren���t significantly changed(r=0.087, p=0.646, r=0.289, p=0.121). CONCLUSION With aging, the aortic annulus increases progressively unlike with mitral annulus. With these results, it is possible to explain the higher prevalence of aortic regurgitation in elderly population.