Objective: This research aims to apply the definition proposed by the Acute Kidney Injury Network (AKIN) research group to assess the incidence, risk factors, and outcomes in acute kidney injury (AKI) patients admitted at the intensive care unit (ICU). Design: This is a retrospective cohort study. Patients who were admitted to the ICU from January 1, 2003 to December 31, 2004 were studied. Interventions: Medical records of all patients were reviewed. Demographic information, diagnoses, risk factors for AKI, laboratory data, urinary output, frequency and days of exposure to mechanical ventilation, ICU and hospital stay, and outcomes were recorded. Measurements and Main Results: A total of 794 patients were studied. There were 39.8% of patients who presented AKI (stage 1: 13.9%, stage 2: 12%, stage 3: 13.9%). The variables that were associated with the presence of AKI in the multivariable analysis were as follows: sepsis (odds ratio [OR], 5.29; 95% confidence interval [CI], 3.36-8.33), heart failure (OR, 3.01; 95% CI, 1.59-5.67), vasopressor use (OR, 1.89; 95% CI, 1.26-2.83), and age (β = 1.02; 95% CI, 1.01-1.03).The mean hospital stay increased with renal commitment: patients without AKI, 10.9 days; AKIN stage 1, 17.8; AKIN stage 2, 21.1; and AKIN stage 3, 22.1 days (P < .0001).Mortality rate increased as more advanced the AKI stage was (no AKI, 7.3%; AKI 1, 16.4%; AKI 2, 34.7%; and AKIN 3, 45.5%; P < .0001). Conclusions: All of the result indicators-stay days in ICU, hospital stay days, frequency and days of mechanical ventilation, and mortality-considerably increased with more acute AKI stage. The most important risk factor of AKI was the sepsis.