Objective: To assess the factors that affect the mortality in acute renal failure (ARF) in children. Patients and methods: We studied 149 patients with ARF and described the findings by age, gender, pathophysiological mechanism of renal damage, and type of renal damage, which can be oligoanuric and/or septic. We used multiple logistic analysis, Cox analysis for survival, and Kaplan-Meier curves. Results: The male/female ratio was 91/58. The most affected age groups were newborns (44.3%) and infants (37.6%). The ARF mechanism was ischemic in 87 cases (58%) and the most frequent clinical type was nonoliguric in 118 cases (79.2%). In the multiple logistic regression analysis, only oliguria (P=0.07) and age group (P=0.049) were associated with mortality. In the survival analysis using the Cox method, oliguria (P=0.003) and sepsis (P=0.03) were associated with mortality. The survival curves showed that the cumulative probability of dying in the first 10, 20, or 40 days after the event was 75, 70, and 45% respectively. When oliguria was present, the survival at day 10 was 47% and when sepsis was present it was 68%. Conclusion: Oliguria, age, and sepsis are factors associated with mortality in children with ARF. © IPNA 2005.