The purpose of this project was to determine the local and overall viscoeleastic properties of the blood vessel wall under physiologic conditions. The local properties were studied in two ways. The compliance of the intimal layer was studied by exposing the surface to a microindentor (metal rod with a prodder tip) and measuring the indentation of the intimal surface as a function of applied force. The strength of the endothelium was studied by exposing the endothelial surface to a saline jet of known strength and quantifying the resulting damage to the endothelial cells. These studies will shed added light on the role of mechanical factors in the pathogenesis of atherosclerosis.