A total of 12 patients previously treated for acute hepatitis of unknown aetiology were retrospectively found to be anti-hepatitis E virus (HEV) IgG-positive. Four patients were anti-HEV IgM- and IgG-positive consistent with an acute HEV infection. All 4 had travelled to or were immigrants from HEV-endemic countries. One anti-HEV IgM-negative patient seroconverted from anti-HEV IgG-negative to positive and 3 from anti-HEV IgG-positive to negative in 2 consecutive serum samples. Of the remaining 4 patients without anti-HEV IgM, 3 had a history of recent travel to an HEV-endemic country. Most patients were young adults and all but 1 recovered from the hepatitis. One patient with a fulminant hepatitis was anti-HEV IgG-positive when tested 4 months after a journey to Turkey. She died from her fulminant hepatitis shortly after admission. All the other patients but 1 normalized their serum liver enzymes within 1-2 months after the onset of disease.