Foot process effacement is the most characteristic change in podocyte structure under a wide variety of human and experimental glomerulopathies with heavy proteinuria. It consists of simplification and even total disappearance of the interdigitating foot process pattern, resulting in the formation of a diffuse cytoplasmic sheet along the glomerular basement membrane. Although abundant evidence related to structural changes in podocyte foot processes has been reported, cellular or molecular mechanisms that occur within podocytes during the development of foot process effacement remain unclear. This review summarizes recent advances concerning structural and functional aspects of foot process effacement in vivo. Following a description of the general morphology of foot process effacement, the role of the cytoskeleton and its related proteins in the effacement are discussed. Finally, the relevance of foot process effacement in glomerular function is considered. Microsc. Res. Tech. 57:241–246, 2002. © 2002 Wiley‐Liss, Inc.