Two cases of Reye's syndrome aged 11 and 13 are reported, confirmed by hepatic biopsy. The favorable outcome observed in the second case seems to be more related with supportive therapy than exsanguinotransfusion and peritoneal dialysis. The physiopathology of this syndrome is not quite clear, but probably in relation with a diffuse mitochondrial insult. Early diagnosis and supportive therapy are important for a favorable outcome.