Early atherosclerotic lesions tend to be found at bifurcations and the curved regions of arteries, and it has been suggested that hemodynamic factors play an important role in the development of lesions. To assess the localization of atherosclerosis at the aorto-renal artery bifurcation, we examined eight cases by intravascular ultrasound. Cross-sectional images at the origin of the renal artery were divided into four segments; cranial, ventral, caudal and dorsal. The thickness of the intima-media complex in each segment, as determined by intravascular ultrasound was measured. The mean thickness of the intima-media complex in the cranial segment was 1.0±0.3 mm, 0.7±0.3 mm in the ventral segment, 0.7±0.2 mm in the caudal segment and 0.7±0.1 mm in the dorsal segment. The mean area of the intima-media complex in the cranial segment was 2.4±0.9 mm2, 1.0±0.1 mm2 in the ventral segment, 0.9±0.1 mm2 in the caudal segment and 1.0±0.2 mm2 in the dorsal segment. There was a significant difference in the thickness and area of intima-media complex between cranial and non-cranial segments. Thus, intravascular ultrasound revealed localization of the atherosclerosis at the aorto-renal artery bifurcation in vivo.