Neuropeptide Y (NPY) is a 36 amino acid amidated peptide which has now emerged as an important regulator of feeding behaviour. Upon intracerebroventricular (icv.) administration, NPY produces a pronounced feeding response in a variety of species. The actions of NPY are believed to be mediated by a family of receptor subtypes named Y1 - y6. Recent studies suggest that the Y1 and Y5 receptor subtypes are intimately involved in NPY induced feeding. This review presents preclinical data obtained with receptor subtype selective agonists and antagonists as well as findings from knockout mice. These new data suggest that NPY receptor antagonists may become an additional option for treating human obesity.