We have studied 64 epileptic subjects aged 2-54 years. The subjects were not hyperuricemic and presented daily or weekly severe seizures not controlled by optimal therapy with antiepileptic drugs maintained at 'therapeutic' plasma concentrations. Allopurinol at doses ranging from 150 to 300 mg daily was added to a preexisting antiepileptic drug treatment which was never modified throughout a study period of 1 year. After about 1 month of therapy, a progressive decrease of the seizure frequency was observed in two thirds of the patients. At the end of follow-up, seizures; were completely controlled in 18.75% of the patients; in 34.37% seizure frequency was reduced by more than 75%; in 15.62% of the subjects, a reduction of the seizure frequency superior to 50% was observed, while 25% of the population studied was unaffected by the treatment and 7.81% worsened.