In 1988, the first report on valproate in migraine prophylaxis was published. Since 1992, 359 patients have been investigated in five double blind studies. Valproic acid was effective in all studies compared to placebo; one study confirmed an effect similar to propranolol. There are no analyses of efficacy in comparison to plasma levels. Adverse events seem to occur somewhat more frequently than in propranolol, but are well known in epilepsy therapy. In the international literature and according to the recommendations of the German Headache Society, valproic acid is a well-established second-choice drug in migraine prophylaxis.