The outcome of patients with acute renal failure (ARF) due to acute tubular necrosis (ATN) was evaluated in this study. Two hundred and twenty-two patients with a mean age of 55.1+/-17.7 years (range 19-97 years; male 153, female 69) who developed ATN in the period from July 1991 through January 1997 were studied. Patients were divided into four groups according to their APACHE II scores at the time of the diagnosis of ATN. Group I included patients with an APACHE II score of 14 or less (n = 70), Group II with a score of 15-18 (n = 52), Group III with a score of 19-23 (n = 58), and group IV with a score of 24 or above (n = 42). The mean APACHE II score for each of the four study groups was 11+/-0.4, 16+/-0.2, 20+/-0.2, and 29+/-0.7, respectively. Patient survival was evaluated by the Kaplan-Meier analysis with censorship at 12 months. Survival rates at 180 days were 67%, 47%, 39%, and zero%, for group I through IV respectively, chi2 = 27.99, p < 0.0001, with a median survival of >365, 120, 31, and 11 days, for groups I through IV, respectively. For patients with oliguria (n = 88) survival at 180 days was 23% vs. 58% for patients without oliguria (n = 134), p < 0.0001, median survival 13 vs. 364 d. Six months survival of those who required dialysis (n = 79) was 25% vs. 58% for those whom dialysis was not needed (n = 143), p = 0.001, median survival 15 vs. 364 d, respectively. In patients with sepsis (n = 58), 6 months survival was 35% vs. 50% for those without sepsis (n = 164), p = 0.013, median survival 14 vs. 169 d. In patients who required mechanical ventilation (n = 72), 6 months survival was 17% vs. 62% for those who did not need respiratory support (n = 150), p = 0.0001, median survival 13 vs. > 365 d, respectively. Finally, 6 months survival in patients with one (kidney only), two, three, and four organ failure was 76, 30, 11, and zero percent, respectively, p = 0.0001, median survival >365, 16, 11, and 12 days, respectively. We conclude that the use of the APACHE II score for the stratification of the severity of illness could be of clinical utility in predicting mortality in patients with ATN. Other predictors of poor prognosis include the need for dialysis, the presence of oliguria, the need for mechanical ventilation, the presence of sepsis, and the number of failed organs.