Objective: Delineation of multiple organ dysfunction syndrome (MODS) is important because of its frequent occurrence in the pediatric intensive care unit and its association with high mortality. However, studies in children are scarce, all have been done in developed countries, and, unlike adult studies, some showed that sepsis is not related to mortality. The aim of this study was to learn about the epidemiology of MODS in our pediatric intensive care unit and to observe if sepsis is associated with mortality. Design: Prospective, observational study. Setting: A 16-bed pediatric intensive care unit. Patients: A total of 269 patients admitted to the pediatric intensive care unit during the study period from August 1996 to January 1997. Interventions: None. Measurements and Main Results: There were 276 admissions (269 patients) during the study period. A total of 156 of them (56.5%) had MODS at some time during their pediatric intensive care unit stay, and 132 (84.6%) of the children had it at the time of admission. There were 71 deaths during the study period, and 65 of them (91.5%) had MODS. The organs less frequently involved were gastrointestinal and hepatic. In children with MODS, 87 had sepsis, and mortality in this group (51.7%) was greater than in those who did not present with sepsis (28.9%, p < .001). A Pediatric Risk of Mortality score of >15 and the presence of sepsis were associated with an increase in mortality risk (odds ratio, 2.8; 95% confidence interval, 1.36 -5.75; and odds ratio, 2.33; 95% confidence interval, 1.18-4.59; respectively). Conclusions: MODS in children usually occurs early, and sepsis increases mortality. Hepatic and gastrointestinal failures are infrequent, and as has been suggested, they could be excluded from the majority of MODS diagnoses. Copyright © 2003 by the Society of Critical Care Medicine and the World Federation of Pediatric Intensive and Critical Care Societies.