In this open-label add-on study of levetiracetam in refractory childhood epilepsy syndromes, we studied the effect of a rapid introduction of levetiracetam on the total seizure frequency in 21 children, known to have partial and generalized seizures. Starting dosage was 10 mg/kg/day, increased every 4th day by 10 mg/kg up to a maximum of 60 mg/kg/day, depending on efficacy and tolerability. In this highly refractory population, 47% showed a seizure frequency reduction of more than 50%. Levetiracetam was effective both in partial and generalized seizures, with a significant effect on myoclonic seizures. Only mild side-effects were observed in four of 21 children, at a dosage of more than 40 mg/kg/day.