OBJECTIVES: To provide an updated version of the Paediatric Index of Mortality 2 for assessing the risk of mortality among children admitted to an ICU. DESIGN: International, multicenter, prospective cohort study. SETTING: Sixty ICUs that accept pediatric admissions in Australia, New Zealand, Ireland, and the United Kingdom. PATIENTS: All children admitted in 2010 and 2011 who were aged less than 16 years at the time of admission and either died in ICU or were discharged. Patients who were transferred to another ICU were not included. Fifty-three thousand one hundred twelve patient admissions were included in the analysis. INTERVENTIONS: None. MEASUREMENT AND MAIN RESULTS: A revised prediction model was built using logistic regression. Variable selection was based on significance at the 95 level and overall improvement of the model s discriminatory performance and goodness of fit. The final model discriminated well (area under the curve, 0.88, 0.88-0.89); however, the model performed better in Australia and New Zealand than in the United Kingdom and Ireland (area under the curve was 0.91, 0.90-0.93 and 0.85, 0.84-0.86, respectively). CONCLUSIONS: Paediatric Index of Mortality 3 provides an international standard based on a large contemporary dataset for the comparison of risk-adjusted mortality among children admitted to intensive care.