Shear　stress　acting　on　the　luminal　surface　of　endothelial　cells　due　to　shear　flow　was　determined　on　a　subcellular　scale.　Three　types　pulsatile　state　flow　(type　I:　nonreversing　flow,　type　II:　reversing　flow,　type　III:　oscillatory　flow)　over　a　wavy　endothelial　cell　surface　was　simulated　by　finite　difference　method.　We　obtained:　(1)　The　shear　stress　amplitude　of　variation　in　pulsatile　field　higher　than　that　in　steady　flowing　field;　(2)　the　fluid　shear　stress　distribution　in　cell　was　nonuniform　and　the　magnitude　of　the　shear　stress　perturbation　depended　on　the　value　of　height/length　ratio,　and　this　value　increased,　with　the　shear　stress　increase;　(3)　the　phase　of　the　shear　stress　distribution　was　also　nonuniform　and　changed　with　time　and　sinusoidal　entrance　velocity,　and　at　the　same　entrance　rate　of　flow,　the　maximum　value　of　shear　stress　in　pulsatile　state　was　much　higher　than　that　in　the　steady　state　condition;　(4)　the　length　growth　of　the　cell　depended　on　the　values　of　average　maximum　shear　stress　on　the　surface;　and　(5)　the　calculated　results　could　be　used　to　explain　the　experiment　results　obtained　by　Helmilinger.