The cause of 636 deaths during acute renal failure (ARF) occurring between 1956 and 1989 were analysed. Deaths due to haemorrhage and to nonrecovery of renal function have declined but cardiovascular deaths and withdrawal of active treatment have increased. The causes of death varied with the clinical situation in which ARF arose. The most important factor contributing to death was the underlying cause of ARF. 67% deaths due to sepsis resulted from infection present at the time of development of ARF. Deaths due to secondary complications have declined, indicating that the precipitating causes of ARF are the main determinant of overall mortality