Microvascular damage occurs in systemic sclerosis and is associated with increased serum levels of endothelial adhesion molecules and endothelium-associated cytokines, including vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1), E-selectin, endothelin-1 and vascular endothelial growth factor (VEGF). Iloprost, a prostacyclin analogue, induces clinical benefit in patients suffering from scleroderma-related Raynaud's phenomenon. This study was performed to investigate the effect of iloprost infusions on endothelium activation. Serum samples from 12 patients with systemic sclerosis were examined using specific enzyme-linked immunoassays. The serum levels of sICAM-1, sVCAM-1 and soluble E-selectin were initially elevated and significantly reduced after iloprost infusions. The serum concentrations of VEGF and endothelin-1 revealed decreased levels after therapy too. These results indicate that the well-known clinical benefit of iloprost infusions on Raynaud's phenomenon is serologically detectable by a reduction of serum levels of endothelium-associated adhesion molecules, cytokines and growth factors reflecting an improvement in endothelial function.