The cause of proteinuria in renal disease is the subject of intensive research and, latterly, the podocyte, a specialized epithelial cell of the kidney glomerulus, has been the focus of much of this endeavour. It is a complex cell with functions and structural features that have an important role in the development of proteinuria. This review explores some of the characteristics of the podocyte and how abnormalities of its structure and function may have particular relevance to the development and progression of clinical diabetic nephropathy.