Febrile seizures are seizures occurring in childhood after the age of one month, associated with a febrile illness not caused by an infection of the central nervous system, without previous neonatal seizures or a previous unprovoked seizure, and not meeting criteria for other acute symptomatic seizures. Febrile seizures are divided into: (a) simple (b) complex, and (c) febrile status epilepticus (FSE). The evaluation and management of the different types of febrile seizures depend on the age and clinical setting of the child that presents with the seizure, as well as the type of the seizures. Prophylactic treatment of a child with febrile seizures using barbiturates or valproate may reduce the number of further seizures, but there is no evidence that this approach alters the probability of developing epilepsy, and the side effects of daily medication are not justified. Much remains to be learned about the pathophysiology of febrile seizures, the biological differences of simple and prolonged seizures, as well as the consequences of the latter. The chapter demonstrates the emerging availability of biomarkers (e.g., imaging) for the consequences of long febrile seizures that might allow clinicians to determine whether a child is at risk of cognitive or pro-epileptogenic sequelae from these prolonged febrile seizures and to treat the children specifically.