The goal of this study was to evaluate the role of Enalapril as an ACE inhibitor on the improvement of headache attacks and clinical status of migraineurs and also on endothelial function as a possible mechanism of their disease. 40 migraineurs were enrolled in this clinical trial study. Migrain were diagnosed on the basis of IHS (international headache society) criteria. Patients were randomized to receive either Enalapril 5mg twice a day or placebo. FMD, blood nitrite, nitrate and CRP as markers of endothelium function and also frequency, severity and duration of headaches using a questionnaire will be measured at baseline and two months after intervention and compared between two groups. After receiving testimonial and 5cc blood, FMD will be measured in both patients and healthy groups. The bloods will transfer to -70c freezer for later nitrite & nitrate & CRP measurement. Second step: The migraineurs will complete a questionnaire about frequency, severity & duration of their headaches. Then we'll randomize the patients in case and control group. Case and control groups will receive 5 mg Enalapril or placebo twice a day for 2 months respectively. After these 2 months the FMD will be measured and 5cc blood will obtain from all of the patients. They should be fast for at least 15 hours before these procedures. All of the data will be measured by the same instruments as before. Again, the migraine questionnaire will complete by patients according to their headaches in these two months.