METHODS A 21-year old woman was referred to the hospital because of progressively deteriorating consciousness. Initially agitation and irritability, later confusion and delirium predominated. Previously influenza with high temperature, headache and vomiting had occurred and been treated with acetylsalicylic acid for some days. Non preliminary diseases were reported. CLINICAL INVESTIGATION: Besides of the deterioration in consciousness no clinical or neurological abnormalities were found. Electroencephalography demonstrated general abnormalities of medium range. Cranial magnetic resonance imaging and liquor investigations showed no pathological findings. In laboratory tests a marked increase of transaminases and ammonia were found. The toxicological screening was normal. METHODS A hepatic encephalopathy due to acute hepatic failure was diagnosed and a detoxication of ammonemia with lactulose was started immediately. Transjugular liver biopsy showed a marked fattening of liver tissue without serological or histological findings for a reason. Because of progressive deterioration in consciousness mechanical ventilation became necessary. Despite of a rapid decline of ammonium serum levels further neurological deterioration occurred. Cranial computed tomography showed oedema of the cerebrum with beginning cerebral occlusion. Despite immediate therapy of cerebral oedema the patient died because of secondary cerebral oedema in hepatic encephalopathy. CONCLUSIONS Reye's syndrome is an acute illness characterized by hepatic encephalopathy and fatty degeneration of the liver. It often occurs after viral infections. After a viral infection that was eventually treated with acetylsalicylic acid Reye's syndrome has to be discussed after exclusion of common causes of hepatic failure.