PURPOSE: It was reported that gene locus for generalized epilepsy with febrile seizures plus(GEFS+) exist in chromosome 19q13.1, and has relationship with a 387 C G mutation in the SCN1B gene. This study is to determine whether there is the 387 C G mutation in the children with GEFS+ and simple febrile seizures(FS). METHODS: The sample group consisted of 16 patients with GEFS+ and 10 patients with FS who were diagnosed by our department of pediatrics from Jan. 1998 to Dec. 1999. The control group consisted of 15 children who do not have seizure disorders. Genomic DNA was extracted from peripheral blood and a segment of the SCN1B exon 3 was amplified by PCR technique. Purified PCR products were treated with restriction enzyme, Hin P1. The restriction pattern was analyzed by sequencing analysis. RESULTS: Sixty nine%(11 of 16) patients with GEFS+ had family history for epilepsy, and epilepsy phonotypes were generalized tonic-clonic seizures in 82%(13 of 16), on the other hand 12%(2 of 16) and 6%(1 of 16) had absences and atonic seizures respectively. EEG findings showed generalized spike and wave in the all patients with GEFS+. in this study, however we could not observe a 387 C-->G mitation of the SCN1B in the children with GEFS+ and febrile seizures. CONCLUSION: The gene for GEFS+ may have a heterogenetic characteristics, and there may be racial differences in mutation frequency. Expanded studies involving large number of different families are required.