Sepsis-induced multiple organ failure (MOF) remains an important cause of child morbidity and death. In over ten years of mechanistic investigation we have reported that organ failure is associated with increased inflammation and coagulation, and reduced immune function. We have characterized three pediatric sepsis- induced MOF syndrome phenotypes; 1) the virus / lymphoproliferative disease associated Sequential Multiple Organ Failure Syndrome, 2) the Compensatory Anti-inflammatory Response / Prolonged Lymphopenia / Immuneparalysis Syndrome, and 3) the microvascular thrombosis related Thrombocytopenia Associated Multiple Organ Failure Syndrome. In our single center, these patients can have a 92% survival when phenotype specific therapeutic strategies are directed to restoring immune and coagulation system function respectively, compared to only a 63% survival when these specific therapies are not used. Because diagnosis of these phenotypes requires specialized diagnostic tests, the characterization of these MOF phenotypes and the use of specific therapies have not been systematically investigated in Pediatric Intensive Care Units, other than our own. The purpose of our proposal is to determine the incidence and outcome of these sepsis induced MOF phenotypes in the Collaborative Pediatric Critical Care Research Network (CPCCRN) population. This proposal will establish the incidence and outcome of these phenotypes, already observed in our Northeastern and predominantly Caucasian population, across the ethnically and geographically diverse CPCCRN population. This knowledge will allow us to determine the feasibility of future trials of phenotype specific therapeutic strategies for pediatric sepsis induced MOF in the CPCCRN. For the past four years we have been one of 6 sites privileged to participate in the CPPCRN. Our principal study during this time was the Critical Illness Stress Induced Immune Suppression Trial which tests the ability of a prophylaxis strategy to prevent stress induced lymphocyte apoptosis and consequent nosocomial infection / sepsis. Our present proposal represents the next step in investigation into the role of immune depression in the ongoing epidemic of nosocomial sepsis and sepsis induced morbidity and mortality