It has been demonstrated that internal jugular vein (IJV) compression aggravates headache intensity in patients of migraine. We hypothesized that patients with migraine may have veins that are less distensible; consequently, these veins are more likely to develop and transmit venous hypertension caused by the increased venous blood volume during IJV compression. We used ultrasonography to measure the extent of venodilatation and distensibility of IJV in response to increased transmural pressure, which was produced by a Valsalva maneuver. The extent of venodilatation were compared between 23 migraine patients (5 men, 18 women; mean age: 40.22+/-12.71 years, range: 27-7 years) and 23 age- and gender-matched normal individuals (5 men, 18 women; mean age: 40.23+/-12.04 years, range: 27-7 years). In the result, the venodilatation of IJV in response to each level of Valsalva pressure in patients with migraine was significantly less than that in normal individuals. Our results suggest that patients with migraine have less compliant IJVs, which makes them susceptible to cerebral venous hypertension. Further studies are needed to elucidate the clinical implications of decreased venous distensibility in migraine patients. (E-mail: hhhu@vghtpe.gov.tw).