Vasoactive intestinal peptide (VIP), a short peptide containing 28 amino acids belonging to the secretin-glucagon family, is initially isolated from the gastrointestinal tract as a potent vasodilator peptide. VIP was initially identified in normal nervous tissue and neurons and was subsequently recognized as a neurotransmitter widely distributed in various tissues. The wide distribution of VIP determines its involvement in a range of biological activities, such as gut motility, hormonal regulation, circadian rhythms, immune responses, and carcinogenesis. The general physiologic effects of VIP include vasodilation, anti-inflammatory actions, cell proliferation, hormonal secretion, regulation of gastric motility, and smooth muscle relaxation; therefore, VIP has emerged as a promising drug candidate for the treatment of several diseases.