GR43175, a selective 5-HT1-like agonist, was administered as oral dispersible tablets in an open, uncontrolled dose-ranging study to assess its efficacy as an agent for acute migraine. Nine patients, all with well established attacks, were assessed for changes in severity of headache and associated symptoms over 2 h. Drug absorption was compared during and between attacks in five patients. Doses of 140 mg and 280 mg resulted in complete relief of all symptoms within 2 h. Treatment was well tolerated in all patients