The　objective　of　our　research　was　to　reveal　the　effects　of　shear　stress　on　the　apoptosis　of　cultured　human　umbilical　vein　endothelial　cells　(HUVECs)　induced　by　lipopolysaccharide　(LPS).　A　parallel-plate　flow　chamber　was　used　to　control　the　strength　and　duration　of　shear　stress　(SS),　and　apoptosis　was　measured　by　immunocytochemistry　and　radio-immunoassay.　Some　important　conclusions　were　drawn.　In　the　stationary　state,　apoptosis　of　HUVECs　could　be　induced　by　LPS　(50　mu　g/ml).　An　SS　of　15　dyn/cm(2)　could　inhibit　the　apoptosis　induced　by　LPS.　However,　an　SS　of　4　dyn/cm(2)　had　less　effect　on　the　same　process.　At　the　same　time,　the　experiment　demonstrated　that　the　increase　in　IL-6　secretion　by　LPS　can　be　inhibited　by　two　different　levels　of　shear　stress.　Moreover,　the　inhibition　effect　was　more　obvious　under　high　level　stress　than　under　low　level.　We　also　found　that　the　effect　of　shear　stress　on　IL-8　was　less　effective　than　on　IL-6.　This　research　provides　data　for　understanding　the　mechanism　of　the　contribution　of　hemodynamic　forces　to　atherosclerosis.　(c)　2005　International　Federation　for　Cell　Biology.　Published　by　Elsevier　Ltd.　All　rights　reserved.