Morphological changes, especially cytoskeletal alterations, in lipopolysaccharide (LPS)-induced vascular endothelial cell injury were studied by using LPS-susceptible bovine aortic endothelial tells (BAEC), BAEC in cultures with LPS showed cell rounding, shrinking, and intercellular gap formation. In those cells, LPS caused the disorganization of actin, tubulin, and vimentin, LPS also induced a reduction in the F-actin pool and an elevation in the G-actin pool, Cytoskeletal disorganization affected transendothelial permeability across the endothelial monolayer, Pretreatment of BAEC with sodium arsenite (SA) prevented alterations in LPS-induced BAEC injury. However, posttreatment with SA had no protective effect on them. SA upregulated the expression of heat shock protein in the presence of LPS, The role of SA in prevention of LPS-induced BAEC injury is discussed.