Body weight homeostasis is regulated by central and peripheral mechanisms, in which cytokines appear to have an important role.The circulating levels of the cytokines interleukin 1 (IL-1) and interleukin 18 (IL-18), and of inflammatory mediators such as prostaglandin E2 (PGE2), amongst others, are elevated in obese individuals. The low-grade inflammation associated with obesity may contribute to the development of insulin resistance, impaired glucose tolerance and type 2 diabetes. This review highlights results of studies in mice which indicate important roles for these proinflammatory cytokines during the development of obesity and insulin resistance, and in the treatment of type 2 diabetes.