Febrile convulsions (FS) are the most common form of seizure in children, occurring in approximately 2-5% of children between 3 months and 5 years of age (up to 6-9% of Japanese children) and are commonly associated with fever caused by bacterial and viral diseases. The International League Against Epilepsy (1993) defines FS as “epileptic seizures occurring after 1 month of age, associated with the disease causing the fever, not due to a central nervous system infection, without previous neonatal seizures or unprovoked seizures, and not meeting the criteria for acute symptomatic seizures.” Most FS are seizures of GTCs, with partial seizures accounting for 4-16%, 87% of seizures shorter than 10 minutes in duration and only 9% longer than 15 minutes, and 5% of seizure durations (>30 minutes), and most are partial. Although most have a good prognosis, one-third of children with FS will have a relapse. The risk of recurrence includes seizures within 18 months, a temperature below 38°C at the time of the seizure, a short fever (<1 hour) before the seizure, and a family history of FS. Seventy-six percent of children with all risk factors had a relapse, compared with 4% of children with no risk factors. Prospective follow-up studies of large samples of children with FS have shown that 2-7% of them develop AFS (Afebrileseizure, AFS) in the future, which is 2-10 times higher than the general population. Risk factors for the development of FS to epilepsy include neurodevelopmental abnormalities, family history of epilepsy, recurrent FS, short duration of fever before FS, and complex FS. Some of these predictors may be genetically related. The odds of developing AFS after 25 years are 2.4% in children without risk factors and 1.4% in the general population. Children with at least 1 complex seizure, a neurological abnormality, and a family history will have a 10% chance of having a seizure at age 7 years, and this risk increases to 21% with long-range FS, and 49% with all three features of complex FS. Retrospective studies have shown that 10-15% of patients with epilepsy have previously had FS. the percentage of those with a history of FS varies by epilepsy syndrome. Although epidemiological studies suggest that FS is associated with future feverless or unprovoked seizures, whether this is causal is currently debated. In animal models, animals that developed long-range FS were significantly more likely to develop limbic system epilepsy, but did not show hippocampal cell loss, unlike human medial temporal lobe epilepsy (MTLE). Therefore, it is inferred that the cause of hippocampal cell loss in MTLE patients is seizures rather than FS.