Two cases of acute hepatic failure are reported in which the diagnosis of Wilson's disease was considered because of low serum ceruloplasmin, low serum copper levels and high 24 h urinary copper. Case 1 had Kayser-Fleischer rings, haemolysis and a high 24 h urinary copper, and so Wilson's disease was confidently diagnosed. Case 2 had high urinary copper excretion, but [64Cu] study indicated a 24:2 h ratio of 0.7 and made the diagnosis of Wilson's disease uncertain. Both patients underwent orthotopic hepatic transplantation, and multiple biopsies were taken from the resected specimen in order to estimate hepatic copper levels. In both cases, hepatic copper levels revealed considerable variation: 0.8-5.2 mumol/g dry wt (case 1) vs 0.02-12.65 mumol/g dry wt (case 2). In case 1, only two of 14 levels were within the diagnostic range for Wilson's disease (greater than 4 mumol/g dry wt), whereas hepatic copper levels in case 2 were in the Wilsonian disease range in three of 16 specimens. These results were in contrast to uniformly high hepatic copper levels in one patient with established cirrhosis secondary to Wilson's disease and two cases of primary biliary cirrhosis. This report indicates that hepatic copper levels vary greatly in acute liver failure, and that estimates from a single biopsy specimen may be misleading as to the cause of the underlying liver disease.