DURING migraine headache the painfully involved vessels, conspicuously temporal artery, are often prominent and tender to palpation.1 Persons who have frequent, severe vascular headaches may have the temporal artery prominent on one or both sides of the head even when headache-free. Major variability occurs in the size and prominence of the temporal artery from day to day, and indeed from hour to hour. These changes are notable in subjects with migraine headache, as contrasted with subjects who seldom or never have headache. Moreover, persons with migraine headache exhibit such cranial vasomotor changes, especially during periods of frequent headache attacks, and particularly during the 18 to 72 hours prior to the headache. These observations suggest that there is greater variability in the contractile state of the cranial arteries in subjects with migraine than in those who seldom or never have headache. Accordingly, long-term studies were undertaken with improved amplifying and