Background: Acute liver failure (ALF) is a rare syndrome of severe, rapid-onset hepatic dysfunction-without prior advanced liver disease-that is associated with high morbidity and mortality. Intensive care and liver transplantation provide support and rescue, respectively. Objective: To determine whether changes in causes, disease severity, treatment, or 21-day outcomes have occurred in recent years among adult patients with ALF referred to U.S. tertiary care centers. Design: Prospective observational cohort study. (ClinicalTrials .gov: NCT00518440) Setting: 31 liver disease and transplant centers in the United States. Patients: Consecutively enrolled patients-without prior advanced liver disease-with ALF (n = 2070). Measurements: Clinical features, treatment, and 21-day outcomes were compared over time annually for trends and were also stratified into two 8-year periods (1998 to 2005 and 2006 to 2013). Results: Overall clinical characteristics, disease severity, and distribution of causes remained similar throughout the study period. The 21-day survival rates increased between the two 8-year periods (overall, 67.1% vs. 75.3%; transplant-free survival [TFS], 45.1% vs. 56.2%; posttransplantation survival, 88.3% vs. 96.3% [P < 0.010 for each]). Reductions in red blood cell infusions (44.3% vs. 27.6%), plasma infusions (65.2% vs. 47.1%), mechanical ventilation (65.7% vs. 56.1%), and vasopressors (34.9% vs. 27.8%) were observed, as well as increased use of N-acetylcysteine (48.9% vs. 69.3% overall; 15.8% vs. 49.4% [P < 0.001] in patients with ALF not due to acetaminophen toxicity). When examined longitudinally, overall survival and TFS increased throughout the 16-year period. Limitations: The duration of enrollment, the number of patients enrolled, and possibly the approaches to care varied among participating sites. The results may not be generalizable beyond such specialized centers. Conclusion: Although characteristics and severity of ALF changed little over 16 years, overall survival and TFS improved significantly. The effects of specific changes in intensive care practice on survival warrant further study.