PURPOSE: This is a clinical study to evaluate the efficacy and safety profiles of topiramate up to 9 mg/kg/day as adjunctive therapy in various refractory childhood epilepsies including Lennox-Gastaut syndrome in Korea. METHODS: Subjects were selected accorting to the following criteria in various childhood epileptic children, refractory seizure even the patients had been on maximal doses of more than at least 2 other anticonvulants, any type of seizure or epileptic syndrome of childhood, those who had been on topiramate more than 6 months. This is a clinical retrospective study performed for 2 years from Feb. 1999 to Feb. 2001 at the Severance hospital pediatric neurological clinic. The topiramate was given the patients as add-on therapy and we observed the seizure frequency, type of seizure, development of any adverse effects, and the difference of result between the idiopathic and symptomatic or cryptogenic group. Of the 238 patients at our clinic on topiramate for 2 years, 114 patients with refractory were enrolled in this study. Those data were analysed with descriptive methods and qui-squares to evaluate the efficacy and safety profiles of topiramate. RESULTS: 60 patients out of 114(52.6%) manifested reduction of seizure occurrence more than 50%, while 12 patients(10.5%) were seizure free. 39 patients(55.7%) out of 70 with partial seizure reduced seizure occurrence more than 50% by add-on therapy and 7 patients(10.0%) had no further seizures. In the group of generalized tonic clonic seizure, 15 patients(57.7%) reduced seizure over 50% and 5(19.2%) had no seizures with add-on therapy. Of patients with Lennox-Gastaut syndrome, 25.0% showed a greater than 50% reduction but no patient proved to be seizure-free. 4 patients with myoclonic seizure did not respond to add-on therapy. There was no difference of seizure frequency both idiopathic and symptomatic or cryptogenic group of partial and generalized tonic clonic seizure. The number of patients manifesting adverse reactions was 48(42.1%) patients in order of frequency, the reactions were somnolence in 26, irritability in 16 and anorexia in 6 patients. CONCLUSION: Topiramate is believed to be an effectsive, safe anticonvulsant when used as adjunctive therapy for various refractory childhood epilepsies. However, patients with Lennox-Gastaut syndrome and myoclonic seizures were reacted less favorably to topiramate.