Pituitary adenylate cyclase-activating polypeptide (PACAP), a neuropeptide belonging to the vasoactive intestinal peptide (VIP)/secretion/glucagon family of peptides, interacts with a distinct high-affinity receptor (type I receptor) on a number of tissues. These PACAP type I receptors have a high affinity for PACAP and a low affinity for VIP and are present in the hypothalamus and anterior pituitary, where they regulate the release of adrenocorticotropin, luteinizing hormone, growth hormone, and prolactin, and in the adrenal medulla, where they regulate the release of epinephrine. Type I PACAP receptors are also present in high concentrations in testicular germ cells, where they may regulate spermatogenesis, and some transformed cell lines, such as the rat pancreatic acinar carcinoma cell AR4-2J. Here we report the molecular cloning and functional expression of the PACAP type I receptor isolated from an AR4-2J cell cDNA library by cross-hybridization screening with a rat VIP receptor cDNA. The cDNA sequence encodes a unique 495-amino acid protein with seven transmembrane domains characteristic of guanine nucleotide-binding regulatory protein-coupled receptors. A high degree of sequence homology with the VIP, secretin, glucagon-like peptide 1, parathyroid, and calcitonin receptors suggests its membership in this subfamily of Gs-coupled receptors. Results of binding studies and stimulation of cellular cAMP accumulation in COS-7 cells transfected with this cDNA are characteristic of a PACAP type I receptor. Cloning of the PACAP type I receptor will enhance our understanding of its distribution, structure, and functional properties and ultimately increase our understanding of its physiological role.