Objective: To determine the incidence and outcome of acute kidney injury (AKI) in hospitalized patients. Design: Prospective, observational. Setting: Tertiary care center in North India. Participants/patients: Inpatients, 1 month to 18-yr-old. Intervention: None. Main Outcome Measures: Incidence of AKI based on the serum creatinine criteria proposed by the AKI Network. Results: During February to September 2008, thirty nine of 108 (36.1%) critically ill patients and 34 of 378 (9.0%) patients who were not critically ill developed AKI (P <0.001); the respective incidence densities were 45.1 and 11.7 cases/1000 patient days, respectively. The maximal stage of AKI was stage 1 in 48 (65.8%) patients, stage 2 in 13 (17.8%) and stage 3 in 12 (16.4%) patients; 11(15.1%) required dialysis. Patients with AKI had a significantly longer duration of hospital stay (9 days vs 7 days, P<0.02) and higher mortality (37% vs 8.7%; hazard ratio, HR 2.73; 95% Cl 1.64, 4.54). Independent risk factors for AKI were young age (HR 0.89; 95% Cl 0.83, 0.95), shock (HR 2.65; 95% Cl 1.32, 5.31), sepsis (HR 3.64; 95% Cl 2.20, 6.01), and need for mechanical ventilation (2.18; 95% CI 1.12, 4.26). Compared to patients without AKI, the mortality was higher for AKI stage 2 (HR 5.18; 95% CI 2.59, 10.38) and stage 3 (HR 4.34; 95% Cl 2.06, 9.16). Shock was an independent risk factor for mortality (HR.10.7; 95% Cl 4.96, 22.98). Conclusions: AKI is common in critically ill children, especially younger patients with septicemia and shock, and results in increased hospital stay and high mortality.