Seven children with absence epilepsy were treated with valproate (VPA). All but one child became free of absence seizures during VPA monotherapy. EEG was recorded for 24 h before start of VPA treatment and repeatedly during treatment. Correlation between plasma VPA concentration and reduction of the number of epileptic discharges was significant. Plasma concentration of 440-660 microM VPA was needed to achieve at least 50% reduction of seizure activity.