Background: Coffee is one of the most likely used foods. Caffeine is one of the substances contained in coffee and is well known to increase blood pressure and peripheral vascular resistance acutely, in part because of sympathetic stimulation. Aortic stiffness is an important for cardiovascular system performance and an indepenent prognosticator of cardiovascular risk. We investigated the acute effect of caffeine on aortic stiffness in young healthy subjects. Methods: We studied the effect of caffeine(180mg) in 22 young healthy subjects according to a randomized placebo-control design during a 3 hour period. They abstained from drinking alcohol-or caffein-containing beverages in the 12 hours before the study. Aortic stiffness was evaluated by carotid-radial pulse wave velocity. Results: Pulse wave velocity increased progressively from 9.39짹1.20 m/sec to 11.51짹1.57 m/sec at 30 minutes after coffee intake(p<0.05). That means an increase in aortic stiffness. No such change was seen with placebo-group. Also, systolic blood pressure increased significantly throughout the study from 90.8짹6.66 mmHg to 114.44짹12.86 mmHg at 60 minutes after coffee intake(p<0.05). Conclusion: These results show an acute unfavorable effect of coffee intake on aortic stiffness and systolic blood pressure. This finding has important implication for impact of coffee intake on cardiovascular risk.