Abstract: In this article, 91 aged cases of ARF observed. the results showed that the maincause of ARF in old age were prerenal failure（56%）. The most common prerenal failure wererenal hypoperfusion seconsary to a reduction in effective circulating volume, the secondary wereinterstitial nephritis due to drugs, infection, radiation in renal failure （34.1%）. In old age, theclinical manifestations were atypical, and the cure rate was lower, and the stage of recovery waslonger than that in other age. The morbidity was increased with the increase in age, and thatmortality was increased significantly in the cases with severe complication such as MSOF。