Vasoactive intestinal peptide (VIP) behaves as an important nonadrenergic–noncholinergic inhibitory transmitter in the lung by potentiating airways smooth muscle relaxation and hydroelectrolytic and mucus secretions, 1 and by inhibiting cell proliferation. 2 Pituitary adenylate cyclase activating peptide (PACAP), a peptide that shares a high structural homology with VIP, is also present in the lung and acts as a potent bronchodilator. 3 Three G-protein coupled PACAP/VIP receptors have been cloned: 4 VIP binds to VPAC1 and VPAC2 receptors, whereas PACAP binds to specific PAC1 receptors but it also recognizes (with the same potency than VIP) both VPAC1 and VPAC2 receptors. Using the cDNA clones and specific antibodies, 5, 6 we have recently shown the expression of the three classes of receptors in human lung. 7 Here we extend our aims to analyze, by immunohistochemistry, the presence and distribution of PAC1, VPAC1, and VPAC2 receptors in human lung.