We followed 419 patients with a first, unprovoked, primarily or secondarily generalized tonic-clonic seizure, randomized to immediate antiepileptic treatment or to treatment only in the event of seizure recurrence. The probability of achieving a 2-year remission was 72 vs 57% at 3 months, 84 to 79% at 3 years, and 85 to 86% at 10 years (p = NS). The probability of entering 5-year remission was 47 to 40, 58 to 58, and 64 to 64% (p = NS). Early treatment does not affect the long-term prognosis of epilepsy.