Endothelial adhesion molecules play an important role in the tissue recruitment of leukocytes in inflammatory conditions such as rheumatoid arthritis. We have investigated the effect of the antirheumatic drug gold sodium thiomalate on adhesion molecule protein and mRNA expression in cultured human endothelial cells. Gold sodium thiomalate inhibited cytokine (TNF, IL-1, IL-4)-stimulated expression of vascular cell adhesion molecule-1 and E-selectin but not intercellular adhesion molecule-1 on endothelial cells. Gold sodium thiomalate also suppressed TNF-stimulated increases in vascular cell adhesion molecule-1 and E-selectin mRNA levels but had no effect on intercellular adhesion molecule-1 mRNA. Thiomalate (mercaptosuccinate), but not gold thioglucose or D-penicillamine, mimics the effect of gold sodium thiomalate at equimolar concentrations. We propose that the inhibition of vascular cell adhesion molecule-1 and E-selectin expression by gold sodium thiomalate is due to its thiomalate and not its gold component. Gold sodium thiomalate has a direct effect on endothelial adhesion molecule expression, and this may contribute to its antiinflammatory activity.