The adenylate cyclase system, which consists of a catalytic moiety and regulatory guanine nucleotide-binding proteins, provides the effector mechanism for the intracellular actions of many hormones and drugs¹. The tissue specificity of the system is determined by the particular receptors that a cell expresses. Of the many receptors known to modulate adenylate cyclase activity, the best characterized and one of the most pharmacologically important is the β-adrenergic receptor (βAR). The pharmacologically distinguishable subtypes of the β-adrenergic receptor, β₁ and β₂ receptors, stimulate adenylate cyclase on binding specific catecholamines¹. Recently, the avian erythrocyte β₁, the amphibian erythrocyte β₂ and the mammalian lung β₂ receptors have been purified to homogeneity and demonstrated to retain binding activity in detergent-solubilized form^1–5. Moreover, the β-adrenergic receptor has been reconstituted with the other components of the adenylate cyclase system in vitro⁶, thus making this hormone receptor particularly attractive for studies of the mechanism of receptor action. This situation is in contrast to that for the receptors for growth factors and insulin, where the primary biochemical effectors of receptor action are unknown. Here, we report the cloning of the gene and cDNA for the mammalian β₂AR. Analysis of the amino-acid sequence predicted for the βAR indicates significant amino-acid homology with bovine rhodopsin and suggests that, like rhodopsin⁷, βAR possesses multiple membrane-spanning regions.