A novel arterial wall stiffness parameter, the Cardio-Ankle Vascular Index (CAVI), was developed to measure the stiffness of the aorta, femoral artery, and tibial artery independently of blood pressure. CAVI is calculated using the formula: CAVI = ln(Ps/Pd) × 2ρ/ΔP × PWV², where Ps and Pd are systolic and diastolic blood pressures, ρ is blood density, ΔP is Ps - Pd, and PWV is pulse wave velocity. This formula was derived from Bramwell-Hill's equation and is used to quantify arterial stiffness. The study evaluated the reproducibility and clinical utility of CAVI in hemodialysis patients. The average coefficient of variation for five measurements among 22 healthy volunteers was 3.8%, indicating good reproducibility. In hemodialysis patients, CAVI was weakly correlated with systolic and diastolic blood pressures, unlike brachial-ankle PWV, which was strongly correlated. CAVI values were significantly higher in patients with atherosclerotic diseases, including those with percutaneous transluminal coronary angioplasty, ischemic changes in electrocardiograms, and diabetes mellitus, compared to those without atherosclerotic signs. CAVI was found to reflect the degree of arteriosclerosis in the aorta, femoral artery, and tibial artery quantitatively. It is not affected by blood pressure, making it a useful tool for assessing vascular stiffness. However, CAVI measures the properties of the entire arterial system, including the aorta, which is elastic, and the femoral and tibial arteries, which are muscular and nerve-controlled. Therefore, vascular stress should be minimized to avoid effects from vasospasms. CAVI is a promising non-invasive index for assessing vascular stiffness and could be used in clinical practice to evaluate arteriosclerosis.A novel arterial wall stiffness parameter, the Cardio-Ankle Vascular Index (CAVI), was developed to measure the stiffness of the aorta, femoral artery, and tibial artery independently of blood pressure. CAVI is calculated using the formula: CAVI = ln(Ps/Pd) × 2ρ/ΔP × PWV², where Ps and Pd are systolic and diastolic blood pressures, ρ is blood density, ΔP is Ps - Pd, and PWV is pulse wave velocity. This formula was derived from Bramwell-Hill's equation and is used to quantify arterial stiffness. The study evaluated the reproducibility and clinical utility of CAVI in hemodialysis patients. The average coefficient of variation for five measurements among 22 healthy volunteers was 3.8%, indicating good reproducibility. In hemodialysis patients, CAVI was weakly correlated with systolic and diastolic blood pressures, unlike brachial-ankle PWV, which was strongly correlated. CAVI values were significantly higher in patients with atherosclerotic diseases, including those with percutaneous transluminal coronary angioplasty, ischemic changes in electrocardiograms, and diabetes mellitus, compared to those without atherosclerotic signs. CAVI was found to reflect the degree of arteriosclerosis in the aorta, femoral artery, and tibial artery quantitatively. It is not affected by blood pressure, making it a useful tool for assessing vascular stiffness. However, CAVI measures the properties of the entire arterial system, including the aorta, which is elastic, and the femoral and tibial arteries, which are muscular and nerve-controlled. Therefore, vascular stress should be minimized to avoid effects from vasospasms. CAVI is a promising non-invasive index for assessing vascular stiffness and could be used in clinical practice to evaluate arteriosclerosis.