BACKGROUND: Juvenile myoclonic epilepsy(JME) is the most common idiopathic generalized epileptic syndrome which occurs mostly in the second decade of life. It is still frequently unrecognized and misdiagnosed. JME responds well to valproate, but is hardly controlled by other commonly used antiepileptic drug such as carbamazepine or phenytoin. We intended to Investigate the clinical symptoms and EEG findings of JME to support the diagnosis and treatment of JME. SUBJECTS AND METHODS: We retrospectively reviewed the medical record of 18 childrens with JME, from March 1991 to February 1997 We have analysed the clinical symptoms, seizure type, EEG findings including photosensitivity, and the effect of antiepileptic drug. RESULTS: 1) Seven patients were boys and eleven patients were girls(M : F=1 : 1.6). The seizure onset between 5 and 7 years of age were noted in 5 cases, that between 8 and 10 years in 5 cases, and in 8 cases seizures began after 11 years of age 2) Generalized convulsive seizures were noted in 16 cases(GTC 13, GC 2, GCTC 1), myoclonic seizures in 18 cases, absence seizures in 5 cases, and photoconvulsive seizures during video game were associated in 3 cases. 3) Epileptiform discharges at the diagnosis of JME were noted 12 cases(66.7%), and no epileptiform discharges were seen in 6 cases(33.3%). The background activities were normal in all cases. In all 12 cases that showed abnormal epileptiform discharge, generalized spike and wave discharges were obtained, and photosensitivies noted in 4 cases. 4) Follow up EEG obtained after treatment, showed normal EEG findings in 16 cases, and abnormal EEG findings were obtained in 2 cases. 5) Sixteen cases responded well to valproate monotherapy, and 2 other cases responded to valproate and ethosuximide combined therapy. In one case who received vigabatrin, the seizure was aggravated. 6) In 5 cases who discontinued antiepicoptic drug medication after 3 year seizure free duration, 3(60%) cases relapsed within 1 year, and 2(40%) cases remained seizure free for over 1 year. CONCLUSION: Juvenile myoclonic epilepsy is an epileptic syndrome with generalized convulsive seizure, myoclonic seizure, and absence seizure, and EEG findings showed generalized spike and wave discharge in 66.7%, and photosensitivity in 22.2%. JME responded well to valproate monotherapy or valproate and ethosuximide combined the rape, but not responded to other antiepileptic drugs.