Cytokines play a key role as communication signals during both normal immunologic responses and pathologic conditions leading to infectious, inflammatory, and neoplastic diseases. Production and biologic function of cytokines are affected by changes in macro- and micronutrients. On the other hand, metabolic and catabolic consequences of the action of cytokines change nutrient status and the distribution of nutrients in tissues. The effect of some nutrients on cytokine production as well as some of the biologic effects of cytokines are mediated through metabolites of arachidonic acid (prostaglandins, leukotrienes, etc.). Other mechanisms involved in nutrient-induced changes of cytokines needs to be determined. Understanding the role of nutrients in cytokine production and biologic function during normal homeostasis, as well as under pathologic conditions, can help in designing proper dietary modification for the prevention and therapy of diseases.