Acute, short-term hyperglycemia is becoming recognized as an important risk factor for several diseases. In the present study, using human aortic endothelial cells (HAECs), we investigated whether short-term high glucose exposure, either on the scale of hours, could enhance the monocyte adhesion and migration to the subendothelium via increasing expression of adhesion molecules and release of chemotactic factors. HAECs stimulated with 25mM d(+)glucose (HG) for not more than 12h, exhibited rapid up-regulation of vascular cell adhesion molecule-1 (VCAM-1) and monocyte chemoattractant protein-1 (MCP-1) mRNA and protein. Although intercellular adhesion molecule-1 (ICAM-1) is considered as a marker of the activation of the atherogenic process, early up-regulation was not observed, and VCAM-1 and MCP-1 protein enhance was sufficient to increase the adhesiveness of human monocytes U-937 to HAECs and their transmigration into the subendothelial space after 4h HG stimulation; both effects were prevented by interfering with monoclonal antibodies against VCAM-1, CD11b, and MCP-1. An increased intracellular oxidative stress, a translocation of NF-kappaB to the nucleus and a prevention of adhesion and transmigration of U-937 by interfering with NF-kappaB inhibitors was also observed after a short HG treatment. Taken together, these results suggest that either acute hyperglycemic spikes could exert an influence on the onset of diabetic complications and on the development of the atherogenic profile on diabetic and non-diabetic subjects.