The chemokine monocyte chemoattractant protein-1 is a potent chemoattractant for monocytes. Monocyte chemoattractant protein-1 is produced by vascular endothelial cells during inflammatory diseases such as atherosclerosis. In this study, we examined the effects of a thiazolidinedione on monocyte chemoattractant protein-1 expression in human vascular endothelial cells. In human vascular endothelial cells, interleukin-1beta and tumor necrosis factor-alpha induced endogenous monocyte chemoattractant protein-1 protein secretion, mRNA expression and promoter activity. The thiazolidinedione inhibited these effects. In summary, our results indicated that the suppression of the expression of monocyte chemoattractant protein-1 can be accomplished by thiazolidinedione treatment, raising the possibility that thiazolidinedione may be of therapeutic value in the treatment of diseases such as atherosclerosis.