[D-Trp34]-Neuropeptide Y is a potent and selective neuropeptide Y (NPY) Y5 receptor agonist. [D-Trp34]-Neuropeptide Y is a significantly less potent agonist at the NPY Y1, Y2, Y4, and y6 receptors. [D-Trp34]-Neuropeptide Y markedly increases food intake in rats.