Cytokines play an important role in inflammation and immunity. In this study, the authors examined expression of macrophage migration inhibitory factor (MIF) in vascular endothelial cells, using human umbilical vein endothelial cells (HUVEC), by reverse transcription-polymerase chain reaction (RT-PCR)/Southern blot, Western blot analysis, and immunohistochemistry. The RT/PCR/Southern blot showed that MIF mRNA was exceedingly upregulated by the stimulation of lipopolysaccharide (LPS) and reached the maximum 12 h after the stimulation. At the range of 10 pg/ml of LPS, the MIF mRNA expression was induced in a dose-dependent manner, but drastically decreased at doses of more than 100 ng/ml. Western blot analysis and immunohistochemistry using an anti-human MIF antibody revealed the presence of MIF protein in cytoplasm of the unstimulated cells. The precise pathophysiological role of MIF in HUVEC has not been fully understood; however, the upregulation of MIF mRNA expression in vascular endothelial cells by LPS stimulation suggests the possibility that the cytokine plays an important role in systemic inflammatory events such as endotoxaemia.