Integrins are heterodimeric cell surface receptors that mediate heterophilic cell-cell interactions and interactions between cells and the extracellular matrix (Hynes RO. Cell 69: 11-25, 1991). As such, they are involved in morphogenetic processes during development, as well as in the maintenance of normal tissue architecture in fully developed organs. Integrins are now recognized to be a large family of receptors, and several different integrins have been demonstrated as being expressed in the developing and adult kidney (Korhonen M, Ylkanne J, Laitinen L, and Virtanen I. Development 122: 3537-3547, 1996; Rahilly MA and Fleming S. J Pathol 167: 327-334, 1992). This review will summarize present knowledge about integrin expression in the developing, normal, and diseased kidney and attempt to provide a hypothetical framework for understanding integrin function in the urogenital system. Since the last time this area was reviewed (Hamerski DA and Santoro S. Curr Opin Nephrol Hypertens 8: 9-14, 1999), there have been significant publications on the roles of integrins in kidney development and disease. At present, there are many more questions than answers, and integrins present an area where many novel and exciting findings will emerge in the coming years.