Single doses of phenytoin (500 and l.OOOmg), carbamazepine (400 and l.OOOmg) and sodium valproate (600mg) were given orally to 5 healthy young volunteers and serum concentrations determined between l-8h after administration. The design was double-blind and placebo-controlled. Serum concentrations considered "therapeutic" were obtained after sodium valproate and the lOOOmg dose of carbamazepine. The results suggest the loading-doses of phenytoin (1500-2000mg) and carbamazepine (800mg) are useful in the subacute control of frequent epileptic seizures on an out-patient basis, and that carbamazepine may be used for lasting control of seizures of status epilepticus treated initially with diazepam or other rapidly-acting preparation.