A review of the patent literature for neuropeptide Y (NPY) antagonists is presented for the period of January 2000 to March 2001. This review focuses on antagonists of the Y(1) and Y(5) receptor subtypes, which have been of primary interest as anti-obesity agents. In contrast to the Y(5) receptor, there have been only a limited number of new chemical entities claimed as antagonists at the Y(1) receptor. This may suggest either a greater interest in the Y(5) subtype as a target for therapeutic intervention or difficulty in finding small, potent, non-peptide antagonists of the Y(1) receptor. Nevertheless, there are subnanomolar antagonists that are selective for both receptor subtypes available, which should prove to be useful in determining the roles of the Y(1) and Y(5) receptors in food intake, energy homeostasis, and other physiological functions.