Generally vascular grafts with a relatively large inner diameter (>5mm) have been successfully employed for replacement in the human body. However, the use of small diameter grafts is limited, because these grafts rapidly occlude due to the thrombosis. the ideal blood-contacting surface of a prosthesis would be an endothelial cell (EC) lining, because the confluent monolayer of healthyl ECs that culture natural blood vessels represents the ideal nonthrombogenic surface. For vascular graft application, the stable EC adhesion on surface under flow conditions is very important. In this study, the adhesive strength of ECs attached on polymer surfaces coated with collagen type IV (Col IV), fibronectin (Fn), laminin (Ln), and treated with corona was investigated onto polyurethane (PU) films. The EC-attached PU surfaces were mounted on parallel-plate flow chambers in a flow system prepared for cell adhesiveness test. Three different shear stresses (100, 150, and 200 dyne/㎠ ) were applied to the flow chambers and each shear stress was maintained for 120 min to investigate the effect of shear stress and surface treatment condition on the EC adhesion strength. It was observed that the EC adhesion strength on the surface-modified PU films was in the order of Ln Fn>Col IV> corona>>control. More than 70% of the adhered cells were remained on surface-modified PU surface after applying the shear stress, 200 dyne/㎠ for 2 hrs, whereas the cells were completely detached on the control PU surface within 10 min after applying the same shear stress. It seems that the type of adsorbed proteins and hydrophilicity onto the PU surfaces play very important roles for cell adhesion strength.