A total of 142 patients (84 per cent aged less than 20 years) with various forms of generalized epilepsy have been treated with sodium valproate alone or in combination with other drugs. The mean duration of symptoms was six years, and half the patients had daily seizures. Nine patients had typical absences, 33 had absences with automatisms, 28 had tonic-clonic seizures with or without photosensitivity, and 72 had various forms of myoclonic epilepsy. Dosage varied from 23 to 54mg/kg and twice-daily administration was usual. Estimation of serum levels did not assist in management. Fits ceased in 63 per cent of all cases and a further 18 per cent showed improvement greater than 50 per cent. Of the 69 with 3c/sec spike-and-wave discharges, 81 per cent became free from all fits, as did 77 percent of those with myoclonic jerks. Fits ceased in eight of the 32 patients with myoclonic astatic epilepsy and there was improvement greater than 50 per cent in a further eight patients. Other anticonvulsants were often withdrawn and always reduced. 21 patients received sodium valproate alone from the start of treatment and all other drugs were withdrawn in another 38. Sodium valproate alone controlled all fits in four children with absences, in 18 with absences with automatisms, 10 with tonic-clonic seizures and 22 with myoclonic epilepsy. Side-effects were rare, mild and often temporary. Potentiation of barbiturates and benzodiazepines occurred, especially clonazepam, which should be avoided. Many patients were more alert. Sodium valproate appears to be the drug of choice for epilepsies associated with generalized spike-and-wave discharges, myoclonic epilepsies or photosensitive epilepsies, and is of especial value in children and mentally retarded patients because it lacks sedating effects and often induces liveliness.