Neuropeptide Y (NPY) is one of the most abundant neuropeptides in the mammalian brain and acts in humans via at least three receptor subtypes: Y1, Y2, and Y5. Whereas selective agonists and antagonists are known for the Y2- and Y5-receptors, the Y1-receptor still lacks a highly selective agonist. This work presents the first NPY-based analogues with Y1-receptor preference and agonistic properties. Furthermore, the importance of specific amino acids of NPY for binding to the Y-receptor subtypes is presented. Amongst the analogues tested, [Phe7,Pro34]pNPY (where pNPY is porcine neuropeptide Y) showed the most significant Y1-receptor preference (> 1 : 3000-fold), with subnanomolar affinity to the Y1-receptor, and Ki values of approximately 30 nM for the Y2- and Y5-subtype, respectively. Variations of position 6, especially [Arg6,Pro34]pNPY and variations within positions 20-23 of NPY were found to result in further analogues with significant Y1-receptor preference (1 : 400-1 : 2000). In contrast, cyclo S-S [Cys20,Cys24]pNPY was found to be a highly selective ligand at the Y2-receptor, binding only threefold less efficiently than NPY. Analogues containing variations of positions 31 and 32 showed highly reduced affinity to the Y1-receptor, while binding to the Y5-receptor was affected less. Inhibition of cAMP-accumulation of selected peptides with replacements within position 20-23 of NPY showed preserved agonistic properties. The NPY analogues tested give insights into ligand-receptor interaction of NPY at the Y1-, Y2- and Y5-receptor and contribute to our understanding of subtype selectivity. Furthermore, the Y1-receptor-preferring peptides are novel tools that will provide insight into the physiological role of the Y1-receptor.