Literature data concerning the comorbidity of migraine and hypertension are conflicting and lacking in consistency. This study was designed to evaluate the distribution of hypertension in a sample of migraineurs in comparison with a group of tension type headache (TTH) patients. Hypertension prevalence was more elevated in headache sufferers than in the general population. This finding might be due to a Berkson's bias; in fact individuals seeking medical care often show a high rate of association between two medical conditions which may be independent in the general population. The highest hypertension prevalence was found in patients with TTH, supporting the hypothesis that this type of headache might be based upon vascular mechanisms.