By screening a cDNA library derived from the A10 rat vascular smooth muscle cell line for functional expression in COS cells, we have isolated a high-affinity receptor for endothelin 1 (Kd = 476 pM) and endothelin 2. The affinity of the cloned endothelin receptor for endothelin 3 is greater than 100 times less in A10 cells and in a CHO cell line stably transformed by the endothelin receptor cDNA. The 426-amino acid receptor polypeptide has seven putative hydrophobic transmembrane domains and is presumed to be a member of the family of guanine nucleotide-binding regulatory (G) protein-coupled receptors. Microinjection of in vitro transcripts of the cloned cDNA into CHO cells confers a transient increase in intracellular calcium in response to endothelin 1, indicating that the receptor is functional and couples to the appropriate G protein(s). RNA analysis reveals high expression in rat lung and heart, tissues known to exhibit binding to iodinated endothelin 1.