Background: High aerobic exercise capacity and sport-related physical activity are reported to be inversely associated with arterial stiffness in healthy young adults. However, it is unknown whether increased physical activity and/or high aerobic exercise capacity reduce aortic stiffness in patients with untreated hypertension. Methods: Subjects with never-treated hypertension were studied [n=84 (55 male); mean age 짹 SD, 49 짹 7 years; age range, 36 ~ 65 years]. Subjects with diabetes, angina, myocardial infarction, major arrhythmia, and cerebrovascular disease or who were taking any cardiovascular medications, including lipid lowering agents, were excluded. Aortic stiffness was measured before exercise testing with pulse wave velocity (heart-femoral PWV, or hfPWV) measurement. Physical activity was estimated using a modified Baecke questionnaire. Aerobic exercise capacity was measured with maximal cardiopulmonary exercise testing (maximum oxygen uptake, or Vo2max). Results: The linear regression analysis showed a significant inverse correlation between sport-index and hfPWV (r = -0.404; P < 0.001), that was independent by multiple linear regression model including, as independent variables, age, gender, body mass index, mean arterial pressure, total cholesterol, fasting blood glucose and heart rate (beta = -0.277; p = 0.004). However, work- and leisure-index, and Vo2max were not associated with hfPWV (p > 0.05). Conclusion: In patients with untreated hypertension, increased physical activity was associated with lower aortic stiffness, but high aerobic exercise capacity was not. These results suggest that daily regular exercise, but not exercise capacity, is an important determinant of aortic stiffness in patients with untreated hypertension.