A novel cDNA clone encoding a putative G protein-coupled receptor has been isolated from a rat aortic smooth muscle cDNA library. Sequence analysis of this clone reveals the structural features characteristic of this superfamily, with a high degree of sequence similarity to the Edg-1 receptor previously reported to be expressed in vascular endothelial cells. This novel receptor mRNA is expressed predominantly in the lung and heart. Although the ligand for this receptor has yet to be identified, the results suggest the existence of a new receptor subfamily in the cardiovascular system thus far unrecognized.