PURPOSE: Febrile seizures affect 2-5% of all children younger than 6 years old. A small proportion of children with febrile seizures later develop epilepsy. Muations in the voltage-gated sodium channel subunit gene SCN1A have been associated with febrile seizures(FSs) in autosomal dominant generalized epilepsy with febrile seizures plus (GEFS+) families and severe myoclonic epilepsy of infancy. The present study assessed the role of SCN1A in familial typical FSs. METHODS: 22 GEFS+ and 62 FSs were selected throughout a collaborative study of Catholic Child Neurology Research Group. The exon 9 region of SCN1A was screened by DHPLC. DNA fragments showing variant chromatograms were subsequently sequenced. RESULTS: A total 84 individuals(22 GEFS+ and 62 FSs) was screened for mutations. Among 22 GEFS+ and 62 FSs patients, five and forty nine showed simple FSs, and seventeen and thirteen had complex FSs. 0% and 8.3% were younger than 12 months old, 22.7% and 46.8% were between 12 and 35 months old, 18.2% and 41.9% were between 36 and 83 months old, and 59.1% and 0% were older than 84 months old. The ratios of male to female were 1.75:1 and 1.82:1. Mutational analysis detected no mutation of SCN1A. Mutational analysis detected eleven silent exonic polymorphisms at G1212A in exon 9 and forty two polymorphisms on intron 9, and 23 intron A/As in 73 homozygote samples. There were no significant differences in allelic frequencies(G/G intron A/A or G/G, G/G intron G/A, G/A intron G/A, reported G/A) of G1212A in SCN1A-exon 9 between the patients with GEFS+ and FSs(31.8% vs. 32.3%, 54.5% vs. 54.8%, 9% vs. 6.5%, 4.5% vs. 6.5%). CONCLUSION: Although our study demonstrated that SCN1A is not frequently involved in GEFS+ and FSs, further systemic research would be necessary.