The prognosis for seizure recurrence was assessed in 133 patients who presented at a median of 1 day after a first-ever tonic-clonic seizure. The cumulative probability of recurrence was 20% by 1 month, 28% by 2 months, 32% by 3 months, 46% by 6 months, 62% by 1 year, and 71% by 3 and 4 years. After a first seizure epilepsy is likely to develop in the majority of patients.