['The aim of this study was to investigate the association between the occurrence of acute kidney injury (AKI) according to pediatric RIFLE (pRIFLE) criteria and adverse outcomes in children after heart surgery.', 'Children undergoing heart surgery in a tertiary hospital in Southern Brazil were followed during their stay in the pediatric intensive care unit (PICU) or until death. The exposure variable was occurrence of AKI according to pRIFLE criteria which place AKI in three categories: R (risk), I (injury), and F (failure). The outcomes studied were death, length of mechanical ventilation (MV), and length of PICU stay.', 'Eighty-five children were enrolled in the study. Of these, 47 (55.3 %) did not have AKI, while 22 (25.9 %), seven (8.2 %), and nine (10.6 %) were classified into pRIFLE categories R, I, and F, respectively. The incidence of death was 18.4 and 4.2 % in patients with and without AKI, respectively. Compared to children who did not develop AKI, the adjusted odds ratio for death was 1.05 [95 % confidence interval (CI) 0.09-11.11], 8.36 (95 % CI 1.32-52.63), and 7.85 (95 % CI 1.53-40.29) in the R, I, and F groups, respectively (p = 0.022). Duration of MV and of PICU stay were significantly higher in those children with AKI.'] Is acute kidney injury according to pediatric RIFLE criteria associated with negative outcomes after heart surgery in children?