The podocyte is the most differentiated cell type in the glomerulum, which forms a crucial component of the glomerular filtration barrier. It has been assumed that podocyte foot processes counteract the elastic force of the glomerular basement membrane and that vasoactive hormones may regulate the contractile state of their foot processes and thereby modulate the ultrafiltration coefficient K(f). Podocyte damage leads to proteinuria, and podocyte injury occurs in many glomerular diseases, which may progress to chronic renal failure. The understanding of the regulation of physiological properties of the podocyte and the mechanisms of its cellular response to injury may thus provide a clue to the understanding of the pathogenesis of proteinuria and glomerular diseases. In the past it was difficult to study cellular functions in this cell type, because of its unique anatomic location and the difficulty in characterizing podocytes in cell culture. However, recent advances in physiological, molecular biological, and cell culture techniques have increased the knowledge of the role of the podocyte in glomerular function. The present review attempts to outline new aspects of podocyte function in the glomerulum.