We report the isolation of the genes encoding the beta 1 and beta 2 adrenergic receptors from dog genomic DNA. Sequence analysis of both genes revealed intronless open reading frames of 473 and 415 amino acid residues, receptively. Heterologous expression of both receptors in CHO cells indicated that both receptors are functionally similar to the human homologs. Comparing the dog beta 1 and beta 2 adrenergic receptors, the beta 1 receptor appears to bind to G proteins more tightly than the beta 2 receptor. Heterologously expressed receptors provide a convenient system for evaluating novel receptor agonists and antagonists.