The PALF study group will collect clinical, epidemiological and outcome data on children with ALF. This information will be used to develop methods to predict whether a child will recover from the illness without the need for a liver transplant or other life-saving procedure. We believe the methods to predict survival will vary with different patient age groups, but that diagnosis, multi-system organ failure, degree of encephalopathy and level of coagulopathy will be important regardless of patient age. Biological samples, such as blood and liver tissue, will provide opportunities to identify subgroups of patients who have unique treatment requirements and outcomes. In addition, we hope to identify unrecognized mechanisms of liver injury resulting in ALF in children. Eligible study participants will be invited to participate in neurocognitive testing. Since patients that develop acute liver failure experience varying levels of hepatic encephalopathy and cerebral edema, we suspect that there may be residual sub-clinical neurological injury that compromises long-term neurocognitive function. Detailed neurocognitive testing has never been performed in a cohort of children that survive acute liver failure and this study seeks to close that information gap by defining the spectrum of neurocognitive outcomes in this population.