Recently, multiple receptors for vasoactive intestinal peptide (VIP) have been molecularly cloned and our understanding of VIP chemistry and mechanisms of action has been broadened. The following review outlines the physiological effects of the hormone from growth regulation, reproduction, bronchodilation, vasodilation and immune interactions to neurotrophism. VIP-based drug design and non-invasive innovative delivery modes are discussed with emphasis on tumor diagnosis and treatment, impotence treatment and neuroprotection.