The risk of recurrence after a single, unprovoked, generalized tonic-clonic seizure was assessed in 119 children aged 2 to 16 years, resident in Normandy and examined at the Hopital General, Le Havre and the Hopital Charles Nicolle, Rouen, France. All children in the study had a normal neurological examination and intellectual development, and the EEG showed no focal abnormality. The risk of recurrence at six months was 22%, at one year 28.5%, at three years 32.6% and at eight years 37.7%. Fifty-eight percent of recurrences occurred within the first six months and 87% within the first two years. The risk of recurrence after two years in patients with EEGs showing spikes or spike-and-wave was 40% and this risk was not significantly different from that for 51 patients with normal EEGs (29%). However, 73% of patients with abnormal EEGs were receiving treatment compared to 52% of those with normal EEGs. Phenobarbital was prescribed for 46 patients, sodium valproate 19, carbamazepine 4, phenytoin 1, Trimedone 1, and phenobarbital and clonazepam 2. Drug compliance was not evaluated. When the seizure lasted less than five minutes, the risk of recurrence at two years was 25% compared with 42% for those whose seizures lasted longer than five minutes. Age at onset of the initial seizure did not affect the risk of recurrence. Seizure duration and history of epilepsy in the family were not significant risk factors. In summary, single, short duration, convulsive seizures of the grand mal type should not be systematically treated, especially when clinical examination and EEG findings are normal. A diagnosis of epilepsy will be confirmed or disproved within two years of follow-up: if seizures do recur they usually do so within that period. A history of febrile seizures does not increase the risk of recurrence of a single unprovoked grand mal seizure. 
COMMENT. Seizures that are focal or associated with mental retardation or brain damage have a higher risk of recurrence and warrant prophylactic treatment with anticonvulsant drugs. A single unprovoked generalized tonic-clonic seizure does not require treatment but medication should be commenced if these seizures recur. In the present study, the cumulative risk of recurrence for treated patients was lower than that of untreated patients but the difference was not significant. One might speculate that the difference may have been significant if compliance with therapy had been monitored and adequate therapeutic drug levels maintained.