Research on hepatic encephalopathy is hampered by the imprecise definition of this disabling complication of liver disease. Under this light, the Organisation Mondiale de Gastroentérologie commissioned a Working Party to reach a consensus in this area and to present it at the 11th World Congress of Gastroenterology in Vienna (1998). The Working Party continued its work thereafter and now present their final report. In summary, the Working Party has suggested a modification of current nomenclature for clinical diagnosis of hepatic encephalopathy; proposed guidelines for the performance of future clinical trials in hepatic encephalopathy; and felt the need for a large study to redefine neuropsychiatric abnormalities in liver disease, which would allow the diagnosis of minimal (subclinical) encephalopathy to be made on firm statistical grounds. In the interim, it proposes the use of a psychometric hepatic encephalopathy score, based on the result of 5 neuropsychologic tests. Finally, the need for a careful evaluation of the newer neuroimaging modalities for the diagnosis of hepatic encephalopathy was stressed.