a 16 year old girl with ulcerative colitis developed hepatitis with a high fever, leukopenia and a marked rise in serum transaminases without jaundice. There were no skin, oral, or genital lesions. Liver biopsy was precluded by abnormalities in coagulation. Postmortem examination of the liver by light and electron microscopy, culture, immunoperoxidase and immunofluorescent staining confirmed the diagnosis of hepatitis due to type 1 herpes simplex virus. Despite the rarity, this viral aetiology should be included in the differential diagnosis of all patients with severe hepatitis. The absence of mucocutaneous lesions should not exclude the diagnosis, especially when other clinical features are compatible.