Randomised clinical trials and systematic reviews of research findings can provide high-quality evidence for decision-making in the management of patients with hepatic encephalopathy. A large number of clinical trials have been undertaken, over the last 50 years, relative to the prevention and treatment of this condition. However, changes have been made, during this time, in the classification of hepatic encephalopathy, diagnostic criteria and assessment measures. These temporally based changes and the consequent lack of standardisation make it difficult to compare interventions and to evaluate their comparative efficacy and safety. While some consensus has been reached in relation to the diagnostic evaluation, classification and monitoring of patients in clinical trials, there is less surety about the choice of clinical endpoints. These outcome measures should be universally applicable, easily measured and clinically relevant. This article reviews the current recommendations regarding outcome selection and outlines some of the potential problems and pitfalls inherent in clinical trial evaluating interventions for the management of hepatic encephalopathy.