To clarify the etiology of accelerated atherosclerosis in patients with diabetes mellitus, we measured expression of intercellular adhesion molecule 1 (ICAM-1), vascular cellular adhesion molecule 1 (VCAM-1), and E-selection on the cell surface by enzyme-linked immunosorbent assay and ICAM-1 mRNA content in human umbilical vein endothelial cells exposed to 5.5 mM glucose (NG), 33 mM glucose (HG), or 27.5 mM mannitol plus 5.5 mM glucose (HM).1) Cell-surface ICAM-1 expression in HG and HM cells was maximally increased by 37% and 32% (P < 0.01), respectively. This effect was dependent on glucose concentration in the medium and was found as early as 24 h and maintained until 6 days after exposing cells of HG. However, neither VCAM-1 nor E-selection expression were affected by HG conditions. 2) Both HG and HM induced increased mRNA content between 6 and 12 h after the stimulation. 3) Adhesion of THP-1 cells to endothelial cells exposed to HG and HM was increased, when compared to NG conditions. These results indicate that osmotic effects can induce increased mRNA and cell-surface expression of ICAM-1 via an as yet unknown mechanism.