Background: The brachial-ankle pulse wave velocity (baPWV) and cardio-ankle vascular index (CAVI) are used to evaluate arterial distensibility. The purpose of this study was to elucidate the acute and chronic effects of smoking on arterial stiffness as measured by baPWV and CAVI. Methods and Results: Ten male smokers were studied to evaluate the acute effect of smoking on arterial stiffness. To elucidate the chronic effect of smoking on arterial stiffness, 160 male active smokers were analyzed. CAVI and baPWV were calculated by measuring the pulse volume record, blood pressure (BP), and vascular length from heart to ankle. CAVI and baPWV were measured using a VaSera VS-1000. In the acute study, baPWV and CAVI increased immediately after smoking 1 cigarette. In the chronic study, baPWV and CAVI significantly correlated with mean BP (MBP) and the Brinkman index. In multiple regression analysis, baPWV independently correlated with MBP, and CAVI independently correlated with the Brinkman index, but not with MBP. Receiver-operating characteristics (ROC) curves of baPWV and CAVI to predict Brinkman index ≥500 demonstrated that the area under the ROC curve of CAVI was higher than that of baPWV. Conclusions: Smoking causes a significant increase in arterial stiffness as measured by baPWV and CAVI. CAVI correlated with the Brinkman index, which suggests that CAVI is a useful index of the degree of arterial stiffness caused by smoking. (Circ J 2011; 75: 698-702)