The results are presented of a follow-up study of 155 Dutch children after the first febrile seizure. Of these initially untreated children 37 per cent had had at least one, 30 per cent at least two and 17 per cent at least three subsequent seizures. The vulnerable period for recurrent seizures after the first febrile seizure was between 12 and 24 months, whereafter the risk was four to five times lower; after any seizure the risk was highest within the first six months, declining steadily after six months without seizures. A first-degree family history of any type of seizure predicted multiple recurrences; an age of at least 30 months and a temperature of greater than or equal to 40 degrees C at initial seizure were associated with reduced risk. Factors in combination influenced the risk of recurrent seizures, sometimes in opposite ways.