In general, acute liver failure (ALF) patients comprise somewhat more women than men, but there is no preponderance of any racial group, other than that expected on the basis of geographic differences. No exclusion will be made on the basis of race, ethnic group or gender. Criteria for inclusion of women and minorities will be those established in the NIH guidelines. Each study site will provide for review a log of patients considered for the NAC study with no identifiers, yielding only gender and age, race and reason for not participating as a check on gender or ethnic bias.