Endothelin-1 (ET-1), the most potent vasoconstrictor yet identified, is a 21 amino acid peptide originally isolated from the culture medium of endothelial cells. This peptide mediates its biological responses by binding to specific cell surface receptors that are located on a number of tissues and cell lines. These receptors belong to the superfamily of seven transmembrane G protein-coupled receptors. Soon after the identification of ET-1, two other closely related peptides (ET-2 and ET-3) were also identified. Based on the different biological effects of these agonists, subtypes of ET receptors (ET_A and ET_B) have been identified, cloned and characterized. This review briefly explains the tissue localization, molecular cloning and regulation of these ET receptors.