C3. Selection of Participants: The attending emergency physician will refer all adult patients who present with a chief complaint of headache during the regular hours of the data collectors. Under the supervision of the site investigators, the data collectors will inform patients about the study and ask for their consent to participate in this study as human subjects. The data collectors will include in this study any patient who has a migraine headache as defined by the International Headache Society (IHS-2003 1.1 migraine without aura; 1.2 migraine with aura). Patients will also be included if they have an IHS probable migraine (IHS-2003 1.6.1 & 1.6.2) [26] that has lasted between 72 and 168 hours. In other words, patients will also be included if their headache meets all IHS migraine criteria except that the duration of the headache has been between 73 and 168 hours. These probable migraine patients will be included because they represent a substantial subset of ED primary headache patients (Friedman, et. al., unpublished data) and because the majority of patients with a disabling probable migraine and a history of similar headaches will respond to migraine-specific medication [27].