Subjects stayed in the study until they had treated one migraine headache with a study patch or two months after randomization, whichever occurred first. During a migraine headache, subjects rated their baseline headache pain severity in a Migraine Study Diary using a 4-point scale (0 = none, 1 = mild, 2 = moderate, 3 = severe) and applied the study patch only if their score was 2 or 3 (i.e., qualifying migraine headache). In addition to headache pain severity, subjects also recorded the presence or absence of aura, nausea, phonophobia, and photophobia, as well as the location of their headache (unilateral or bilateral) and whether their headache increased with movement.