The authors present a retrospective study of 50 patients with hepatic encephalopathy treated at the University Hospital, Faculty of Medicine of Ribeirão Preto since 1959 and discuss clinical, laboratory and anatomo-pathologic aspects. The diagnoses of the different types of liver disease as well as the factors that triggered the episodes of hepatic coma and pre-coma are reported and the role of the measurement of arterial blood gases in establishing the diagnosis is emphasized.