Neuropeptide Y (NPY) consists of 36 amino acids and is one of the most abundant peptides in the peripheral and central nervous system. Several subtypes of NPY receptors have been described (Y1-ye) using segments and analogues of NPY. The Y1-, Y2-and the Ys-receptor, which have been cloned, belong to the G-protein coupled hormone receptor family and will be specially addressed, because they are the endogenous binding sites of neuropeptide Y in human. In contrast, Y4-receptors recognize endogenous PP, Y3-receptors are discussed controversially and the ye-receptor is truncated in human. In this review, we summarize the data of neuropeptide Y with respect to ligand binding, selectivity, receptor structures and ligandreceptor complexes by using ligand analogues, site directed mutagenesis and photoaffinity labeling.