The effectiveness of intravenous lidocaine for relief of vascular headache was assessed using a single-blind protocol. Patients with acute pain due to common migraine or cluster headache were studied and compared with patients with cranial pain of other causes. Pain intensity was measured using a visual analog scale. In 13 headache patients, an intravenous injection of lido- caine (100 mg standard dose) produced rapid relief of clinical pain, with an associated significant change in visual analog scale scores (p < 0.001). Relief lasted approximately 20 min; in most patients the pain then returned to pretreatment levels. No significant side effects were reported by the subjects. This response may be the result of a direct, anesthetic action of lidocaine on trigeminal nociceptive afferents innervating cranial blood vessels.