We have investigated the expression of integrin chains by human renal epithelial cells during in vivo renal differentiation and in vitro cell culture on different extracellular matrices. Using the immunoperoxidase technique to visualize the binding of monoclonal antibodies to different integrin chains in fetal and adult kidneys, we found a change during development from a1ß1, a3ß1, and a4ß1-positive blastemal cells to a2ß1, a3ß1, and a6ß1-positive epithelial cells. The pattern of integrin expression correlates with the presence in the extracellular matrix of the appropriate ligands. In in vitro cell culture experiments, renal epithelium expressed a3 and a5 integrins on all extracellular matrices. Integrins a2 and a6 were found only in cells grown on a laminin-containing substratum. Fibronectin and a5 integrin co-localized on the ventral surface of cells grown on a laminin substratum and at the periphery of cells on glass coverslips. These results suggest that there is a close relationship between integrin a chain usage and the presence of appropriate ligands in the extracellular matrix.