Endothelial sequestration of circulating monocytes is a key event in early atherosclerosis. Hemodynamics is proposed to regulate monocyte-endothelial cell interactions by direct cell activation and by establishment of flow environments which are conducive or prohibitive to cell-cell interaction. We investigated fluid shear regulation of monocyte-endothelial cell adhesion in vitro using a disturbed laminar shear system that models in vivo hemodynamics characteristic of lesion-prone vascular regions. Human endothelial cell monolayers were flow-conditioned for 6 hours prior to evaluating monocyte adhesion under static and dynamic flow conditions. Results revealed a distinctive, clustered-cell pattern of monocyte adhesion which strongly resembles in vivo leukocyte adhesion in early and late stage atherosclerosis. Clustered-monocyte cell adhesion correlated with endothelial cells co-expressing ICAM-1 and E-selectin, as result of a flow-induced selective up-regulation of E-selectin expression in a subset of ICAM-1 expressing cells. Clustered-monocyte cell adhesion assayed under static conditions exhibited a spatial variation in size and frequency of occurrence demonstrating a differential regulation of endothelial cell adhesiveness by the local flow environment. Dynamic adhesion studies conducted with circulating monocytes resulted in clustered-cell adhesion only within the disturbed flow region, where the monocyte rate of motion is sufficiently low for cell-cell interaction. These studies provide evidence and reveal mechanisms of local hemodynamic regulation of endothelial adhesiveness and endothelial-monocyte interaction leading to localized monocyte adhesion, potentially contributing to the focal origin of arterial diseases such as atherosclerosis.