OBJECTIVE: Multiple organ dysfunction syndrome is the main cause of death in adult ICUs and in PICUs. The PEdiatric Logistic Organ Dysfunction score developed in 1999 was primarily designed to describe the severity of organ dysfunction. This study was undertaken to update and improve the PEdiatric Logistic Organ Dysfunction score, using a larger and more recent dataset. DESIGN: Prospective multicenter cohort study. SETTING: Nine multidisciplinary, tertiary-care PICUs of university-affiliated hospitals in France and Belgium. PATIENTS: All consecutive children admitted to these PICUs (June 2006-October 2007). INTERVENTION: None. MEASUREMENTS AND MAIN RESULTS: We collected data on variables considered for the PEdiatric Logistic Organ Dysfunction-2 score during PICU stay up to eight time points: days 1, 2, 5, 8, 12, 16, and 18, plus PICU discharge. For each variable considered for the PEdiatric Logistic Organ Dysfunction-2 score, the most abnormal value observed during time points was collected. The outcome was vital status at PICU discharge. Identification of the best variable cutoffs was performed using bivariate analyses. The PEdiatric Logistic Organ Dysfunction-2 score was developed by multivariable logistic regressions and bootstrap process. We used areas under the receiver-operating characteristic curve to evaluate discrimination and Hosmer-Lemeshow goodness-of-fit tests to evaluate calibration. We enrolled 3,671 consecutive patients (median age, 15.5 mo; interquartile range, 2.2-70.7). Mortality rate was 6.0% (222 deaths). The PEdiatric Logistic Organ Dysfunction-2 score includes ten variables corresponding to five organ dysfunctions. Discrimination (areas under the receiver-operating characteristic curve = 0.934) and calibration (chi-square test for goodness-of-fit = 9.31, p = 0.317) of the PEdiatric Logistic Organ Dysfunction-2 score were good. CONCLUSION: We developed and validated the PEdiatric Logistic Organ Dysfunction-2 score, which allows assessment of the severity of cases of multiple organ dysfunction syndrome in the PICU with a continuous scale. The PEdiatric Logistic Organ Dysfunction-2 score now includes mean arterial pressure and lactatemia in the cardiovascular dysfunction and does not include hepatic dysfunction. The score will be in the public domain, which means that it can be freely used in clinical trials.