Endothelin is a potent vasoconstrictor peptide produced by vascular endothelial cells. Incubation of the serum-deprived confluent porcine aortic endothelial cells with 10–300 pM TGF-β1, resulted in a several fold increase in endothelin mRNA levels with a peak time of 2 h. An enzyme-linked immunosorbent assay revealed that the levels of endothelin in endothelial cell conditioned media was also increased by TGF-β1. These results suggest that TGF-β1, secreted by activated platelets, is involved not only in wound healing, but in the regulation of local vascular tone by stimulating endothelin production in the endothelial cells.