Since the discovery of the protein product of the ob/ob gene, leptin, knowledge of the neurochemical pathways involved in the regulation of feeding has increased enormously. Our understanding of the mechanisms regulating food intake in man has also progressed greatly over a similar time span. Previous research into the regulation of food intake has largely proceeded through a reductionist approach, defining ever-smaller components of these mechanisms. This research strategy has been very productive and instructive, and has yielded a great deal of information on the specific putative components linking energy status and food intake. However, to fully understand the regulation of feeding it is important that these components are systematically reconstructed to investigate relevant interactions. In the present review recent data relating to interactions between systems proposed to be involved in feeding regulation will be highlighted. The review will be directed predominantly (but not exclusively) towards the regulation of human feeding.