Acute liver toxicity caused by carbamazepine is a well known though infrequent event. Severe toxicity with hepatocellular insufficiency is even more rare. A case is presented of a patient who suffered of partial epilepsy on treatment with valproate and carbamazepine, who was admitted because of severe acute liver insufficiency attributable to carbamazepine. He had started treatment with the latter drug two weeks earlier, when he developed fever, jaundice, rash and signs of encephalopathy in association with elevation in serum transaminases levels and a decrease in prothrombin index (24%). Discontinuation of both antiepileptic drugs, together with the usual supportive measures, was followed by a complete resolution. Valproate was restarted without complications. Liver biopsy suggested acute hepatitis of drug-related origin. Granulomas or steatosis were not found. The histologic picture together with the relation between carbamazepine administration and the development of hepatotoxicity allow us to dismiss valproate as the possible causal agent of this patient's disease. Therefore, we believe it was an acute hepatocellular failure secondary to carbamazepine.