Acute Kidney Injury (AKI) is a common complication of critical illness and is associated with high mortality and has a separate independent effect on the risk of death. The incidence of AKI in hospitalized patients ranged from 2-5%, while the incidence of AKI in the ICU varies from 2.5 to 15 %, and mortality in this setting can be as high as 78% in patients who require dialysis. AKI carries high morbidity, increases the length of hospital stay, increases hospital costs and is an independent risk factor for poor outcome in critically ill patients. The aim of this study was to investigate the prognostic value of RIFLE criteria in prediction of outcome of intensive care unit patients with acute renal failure, and its correlation with established older ICU scoring systems as APACHE II and SOFA scores. An experimental prospective, randomized clinical trial was conducted, 60 patients met inclusion criteria were enrolled in the study from the period Jun. 2019 to Dec 2019. The APACHE score of failure subgroup was significantly higher in comparison to risk and injury subgroups (p=0.002). The SOFA score of failure subgroup was significantly higher in comparison to risk and injury subgroups (p=0.001). Regarding Outcome, the main difference between the groups was statistically significant, (p=0. 002) Patients who progress to higher RIFLE classes have higher mortality and longer ICU stay in comparison to patients who did not progress.