In the National General Practice Study of Epilepsy 564 patients classified as having definite seizures have been followed up for 2-4 years. 67% (95% confidence interval 63-71%) had a recurrence within 12 months of the first seizure, and 78% (74-81%) had a recurrence within 36 months. Seizures associated with a neurological deficit presumed present at birth had a high rate of recurrence (100% by 12 months), whereas seizures that occurred within 3 months of an acute insult to the brain, such as head injury or stroke, or in the context of an acute precipitant such as alcohol, carried a much lower risk of recurrence (40% [29-51%] by 12 months). Other factors affecting the risk of recurrence were age-the highest risk being for patients under the age of 16 (83% [77-89%] by 36 months) or over the age of 59 (83% [76-90%] by 36 months-and type of first seizure-the risk of recurrence being much higher for patients with simple partial or complex partial seizures (94% [90-99%] by 36 months) than for those with generalised tonic clonic seizures (72% [67-77%] by 36 months).