Immune activation occurs in response to noxious stimuli such tissue injury, infection, inflammation and malignant neoplasia with the production of cytokines both in the circulation and the central nervous system (CNS). In addition to their fundamental immune functions, cytokines such as the interleukins (ILs), interferons (IFNs) and tumour necrosis factor-a also elicit significant pathophysiological effects on feeding behaviour and play prominent roles in the anorexia and cachexia syndrome often seen in chronic disease states. There is now compelling evidence that demonstrates that an important site of cytokine bioactivity is located within the hypothalamus where they appear to modulate appetite and energy homeostasis. Hypercytokinaemia has also been observed in the obese state where it has been proposed that they may play pivotal roles in mediating the detrimental components of the metabolic syndrome including insulin resistance, impaired glucose tolerance, hypertension, dyslipidaemia and increased cardiovascular risk. This review summarises these putative roles of various cytokines in the regulation of feeding in the setting of anorexia-cachexia and obesity.