Objectives 1) To determine whether pRIFLE (Pediatric Risk, Injury, Failure, Loss, End Stage Renal Disease) criteria serves to characterize the pattern of Acute Kidney Injury (AKI) in critically ill pediatric patients; and 2) to identify if pRIFLE score will predict morbidity and mortality in our patient´s cohort. Design Prospective Cohort. Setting Multidisciplinary, tertiary care, 10- bed PICU. Patients 266 patients admitted to PICU from November 2009 to November 2010. Interventions None. Measurements and Main Results The incidence of AKI in the PICU was 27.4%, of which 83.5% presented within 72hrs of admission to the PICU. Patients with AKI were younger, weighed less, were more likely to be on in fluid overload ≥10%, and were more likely to be on inotropic support, diuretics or amino glycosides. No difference in gender, use of other nephrotoxins, or mechanical ventilation was observed. Fluid overload ≥10% was an independent predictor of morbidity and mortality. In multivariate analysis, AKI-Injury and Failure categories, as defined by pRIFLE, predicted mortality, hospital length of stay, and PICU length of stay. Conclusions In this cohort of critically ill pediatric patients, AKI identified by pRIFLE and fluid overload ≥ 10% predicted increased morbidity and mortality. Implementation of pRIFLE scoring and close monitoring of fluid overload upon admission may help develop early interventions to prevent and treat AKI in critically ill children.