As part of an approach to uncover the brain mechanisms underlying the regulation of energy balance in broiler chickens, we investigated the possible role of neuropeptide Y (NPY). The NPY gene expression was measured in the hypothalamus of birds from a standard Ross male line and a Ross relaxed line. Both lines are derived from the same founder stock, but the relaxed line has not been selected for rapid growth since 1976. Birds of each line consumed feed either ad libitum or according to a standard commercial restricted feeding program. All groups of birds were killed at an average body weight of 2.4 kg. The NPY mRNA levels were significantly increased (P < 0.0001) in feed-restricted birds of both lines relative to ad libitum controls. No significant differences were detected between the lines. These results show that NPY gene expression in the broiler hypothalamus is sensitive to changes in energetic status, as it is in mammals. However, the maintenance of selection pressure for high growth rate is not associated with altered hypothalamic NPY mRNA levels in the ad libitum or restricted state.