Sixty-one newly diagnosed epileptic patients with generalized tonic-clonic, clonic, or tonic seizures were randomly allocated to treatment with valproate (VPA) and phenytoin (PHT). After 6 months, both drugs had been effective in preventing recurrence of seizures. Seventy-three percent of patients receiving VPA and 47% of patients receiving PHT had no recurrences. Side effects of either drug were mild. Laboratory abnormalities were similar for both drugs. Except for one PHT patient with toxic hepatitis, therapy was not discontinued.