Effect of fluid shear stress on permeability of endothelial monolayer was investigated using an endothelial cell (EC)-smooth muscle cell (SMC) cocultured model (CM). Permeability of ECs to bovine serum albumin was measured after exposure to shear stress of 1.5Pa for 48 hours. Morphology and VE-cadherin expression of ECs in CM was almost same as of ECs cultured alone (monocultured model, MM). Under static condition, EC permeability was 5.1±3.0 × 10^-6cm/sec (mean±SD) in MM and 6.5±3.4 × 10^-6cm/sec in CM. After exposure to shear stress, EC permeability in CM (2.2±1.9 × 10^-6cm/sec, p < 0.05) significantly decreased compared with the static model. However, EC permeability in MM (3.9±3.2 × 10^-6cm/sec) did not significantly change compared with static cultured condition. These results suggested that cellular interactions between ECs and SMCs have important influences on EC permeability.