Acute renal failure (ARF) is a common complication in hospitalized patients, but little is known about the epidemiology of ARF in China. In this study, we performed a prospective examination of the cause, prognosis, and risk factors associated with ARF at a hospital in Shanghai, China. We considered all ARF patients who were admitted to our hospital from December 2003 to December 2006. Among the 320 ARF patients, 135 (42.2%) were over the age of 60. Sepsis, heart failure, and nephrotoxic drug use were the leading causes of ARF. The overall mortality rate was 31.9%, and mortality rate was significantly higher among the elderly. Logistic regression indicated that heart failure, respiratory failure, and malignant cancer were risk factors independently associated with poor prognosis. In this Shanghai hospital, there was a high incidence and mortality rate of patients hospitalized with ARF. The prognosis of patients who underwent renal replacement therapy was better than those who were treated more conservatively.