Cytokines play pivotal roles in most physiologic and pathologic processes. This paper reviews recent data on the role of cytokines in mediating renal inflammatory diseases. These data show that cytokines are involved in every phase of inflammatory injury. Cytokines induce expression of major histocompatibility complex class II and adhesion molecules on renal cells and are thereby involved in antigen presentation and leukocyte localization. Cytokines also induce the synthesis of leukocyte chemoattractants, eg, interleukin-8 and monocyte chemotactic peptide-1, in renal cells. Finally, cytokines, and in particular, platelet-derived growth factor and transforming growth factor-β, appear to play a role in the long-term consequences of renal inflammation such as the induction of cell proliferation and the accumulation of extracellular matrix, both of which characterize glomerular and tubulointerstitial fibrosis. Better understanding of the disturbances of the cytokine network in renal inflammation may ultimately lead to novel therapeutic approaches to renal disease.