Acetaminophen is a dose-dependent toxin. Prognosis in severe acute liver injury is related presumably in part to the dose ingested. We sought to assess the value of acetaminophen dosing information in patients with acute liver failure due to acetaminophen toxicity to determine the role of dose as a prognostic indicator. Methods: Prospective data from 113 acute liver failure patients having single time point ingestions of acetaminophen were analyzed. Multivariate and chi-square tests were used to determine the relationship of dose to clinical outcome. We also used the Mann-Whitney U test to compare prognosis and survival in ALF with acetaminophen dose ingested. Results: Multivariate and chi-square analysis failed to show any relationship between acetaminophen dose and spontaneous survival. A separate analysis showed no correlation between acetaminophen dose and clinical prognostic indicators. Conclusions: Dose of acetaminophen ingested did not seem to play a role in prognosis. The most important prognostic factor was coma grade on admission to study. Acetaminophen dosing information is not always obtainable. When it is, it adds little to the clinical assessment. Severity of encephalopathy is a more reliable indicator of prognosis in these critically ill patients. Keywords: acetaminophen; acute liver failure; hepatology; xose; outcome; survival; toxicity