Febrile seizures are the most common seizures in childhood. They have been observed in 2-5% of children before the age of 5, but in some populations this figure may increase to 15%. It is a common cause of pediatric hospital admissions and cause of anxiety for parents. Febrile seizures could be the first manifestation of epilepsy. About 13% of epileptic patients have a history of febrile seizure, and 30% have had recurrent febrile seizures. Their phenotypic characteristics allow, in the majority of cases, a classification of the seizure, an elaboration of a prognosis and to assume a specific therapeutic attitude. It is possible to describe a spectrum according to their severity, from the benign simple seizure to the more complex, febrile seizure plus, Dravet'syndrome, and FIRES. During the past decade, molecular genetic studies have contributed to the identification of genetic factors involved in febrile seizure and related disorders, making the necessity of a careful follow up of these patients in order to detect risk factors earlier. We have reviewed the medical literature to update current knowledge of febrile seizures, their prognosis and their relation to new epileptic syndromes.