The aim of this study is to investigate the associations between febrile seizure and serum levels of vitamin B-12, folic acid, and homocysteine. One hundred and four children who presented with febrile seizure and 75 controls who presented with febrile illness unaccompanied by seizure were enrolled into the study. Mean levels of vitamin B-12, folic acid and homocysteine were compared between two groups. Mean vitamin B-12 level in the febrile seizure group was significantly lower than the control group. The febrile seizure patients with 3 or more had significantly lower serum folic acid than the subgroups with two or one episode only. Serum concentrations of folic acid were significantly lower in the febrile seizure subgroup with body temperature 37.5-39.0 degrees C at time of convulsion. Low serum vitamin B-12 may reduce a child's threshold for seizure and may be a risk factor for febrile seizure. Low serum folic acid level may be predisposed to recurrent febrile seizure.