Apoptosis or programmed cell death is a major focus of interest in many fields of research. Recent advances include definition of key molecules driving the cell death programme, including Fas and Fas-ligand in the plasma membrane, and cytoplasmic proteases such as interleukin-1β-converting enzyme. These are kept in check by 'survival' signals conferred by exogenous cytokines and the extracellular matrix, or by endogenous proteins encoded by the bcl-2 gene family. Important insights into the programme of mammalian cell death have come from comparative biology. The scene is now set for study of apoptosis in renal health and disease, in which recent studies indicate key roles in remodelling of both glomeruli and tubules after renal injury.