Amantadine hydrochloride has been shown in several open studies to benefit children with refractory generalized epilepsy. We used amantadine as adjunctive therapy in 10 adolescents and adults with generalized tonic-clonic, myoclonic, or absence seizures refractory to therapeutic levels of valproate, carbamazepine, phenytoin, and benzodiazepines. Seven patients were men and 3 were women aged 18-29 years, and 8 of 10 patients were mentally retarded. All patients had generalized epileptiform paroxysms on EEG, with generalized or absence seizure recorded in 9. Five patients had both absence and tonic-clonic seizures, and 2 had all three seizure types. Amantadine was added to the existing regimens in weekly increments to 400 mg/day. Two patients had greater than 90 per cent seizure reduction, both with vomiting and somnolence. Two patients had seizure reduction between 50 and 90 per cent, 1 with anorexia and sleepiness. Three patients had no change in seizures, and 3 had worse tonic-clonic seizures. Amantadine may have some antiepileptic efficacy of unknown mechanism, but it may worsen generalized tonic-clonic seizures and is likely to be of limited value in adults.