We quantified radial artery atherosclerosis by intravascular ultrasound (IVUS) and determined the relationship between established cardiovascular risk factors and the extent of atherosclerotic plaque. Intravascular ultrasound examination of the radial artery was performed in patients undergoing transradial angiography or intervention. Total 50-mm segments starting at the radioulnar bifurcation were analyzed at 2-mm intervals to compute atheroma volume. In 115 consecutive patients, atheroma volume averaged 67.4 mm(3) and percentage atheroma volume was 25.2%. Radial arteries showed age-related acceleration of atherosclerosis. Total atheroma volume was strongly associated with square of age and male gender. Hypertension and diabetes were strong independent predictors of larger radial artery atheroma burden. Radial artery atherosclerosis, which can be quantitatively analyzed by IVUS, could be used as a surrogate marker for atherosclerosis.