An intravascular ultrasonic imaging device (40 MHz) was used to obtain in vitro ultrasonic images and matching histologic cross-sections, derived from human vascular specimens. The feasibility of assessing vessel wall morphology as well as the ability to accurately document plaque thickness was determined. Based on the echogenicity of the arterial media, intravascular ultrasound could distinguish muscular arteries from elastic arteries, veins, and bypass grafts. The hypoechoic media only present in the muscular type of artery proved to be an essential landmark to document superimposed atherosclerosis. Plaque thickness calculated in these arteries showed close relationship with the corresponding histologic cross-section. Using real-time in vivo intravascular imaging (30 MHz), the morphology of the vessels interrogated was studied. The dynamic change of the arterial wall, as well as the outcome after intervention, is discussed.