Objective To investigate the etiology and prognosis of acute renal failure in the elderly. Methods One hundred and sixteen ARF patients in our hospital from Jan,1998 to Oct,2003 were divided into two groups: senile group (≥65years old), control group(<65years old). The causes and prognosis of the two groups were analyzed. Results The main causes of acute renal failure in the elderly were as follow, infection (32.3%), drugs(18.3%), volume depletion(14.0%) and cardiovascular disease(12.7%).The incidence and mortality rate of ARF in senile group were higher conpared to the control group. It related with the severity of primany disease and the function of organs. Conclusion Both the incidence and mortality rate of acute renal failure in the elderly are high, early diagnosis and early treatment may be beneficial to improving the prognosis of ARF.