The aim of this study is to compare the efficacy of magnesium with sodium valproate as prophylactic therapy in adult patients with a diagnosis of migraine headache based on the latest International Headache Society criteria. Study design is randomized, double-blind and prospective. These subject (228 patients) will be entered in the study with a personal satisfaction with regard to the inclusion and exclusion criteria and will be assigned randomly into one out of three groups: 250 mg twice a day magnesium oxide (n=76), 200 mg twice a day sodium valproate (n=76), magnesium oxide (250 mg twice daily) and sodium valproate (200 mg once per day) concurrently (n=76). The study duration from beginning of drug prescription will be 3 month. The primary objective of the study is to compare the frequency and severity of migraine headaches based on Wong-Baker Faces Pain Rating Scale at the end of month 1, 2 and 3 in three groups. Follow up visits will be scheduled every 4 weeks to 12 weeks. To evaluate blood and liver side effects of drugs, CBC, diff, AST, ALT tests will be performed at the start of therapy and the end of 12 weeks of the study. Finally, the severity, frequency, duration of headache, side effects and amount of analgesics needed during a migraine attack will be compared in the two groups.