While studies have noted possible benefits of valproate for migraine prophylaxis, most have small study samples (range 22-34 patients). The more recent, larger clinical trial confirms the effectiveness of valproate in the prevention of migraines. The available evidence suggests that valproic acid should provide another alternative to conventional migraine prophylaxis. However, it would still be beneficial to see other large studies conducted to determine valproate's place among the migraine prophylactic therapies currently available. The Food and Drug Administration recently approved divalproex sodium for the prevention of migraine headaches. The usual starting dosage is 250 mg bid, titrating to 1000 mg/d if necessary.