3. Patients with 4-20 qualified migraine attacks per month over the past three months prior to Screening, as well as during the four weeks of the Baseline Phase will be eligible for entry into this study. The interval between two qualified migraine attacks should be at least 24 hours to be counted as distinct migraine attacks. A qualified migraine attack without aura is defined as a headache that lasts 4-72 hours (if untreated or unsuccessfully treated) or if successfully treated. This attack has at least two of the following characteristics: unilateral location, pulsating quality, moderate or severe intensity that inhibits or prohibits daily activities or aggravation by routine physical activities such as walking up stairs. In addition, at least one of the following symptoms must be present during the headache: nausea, vomiting, or photophobia and phonophobia. A qualified migraine attack with aura must fulfill the same criteria as the headache attack, plus have an associated aura as defined by the Migraine Criteria of the Headache Classification Committee of the International Headache Society. An aura alone that requires acute migraine treatment will also be considered a migraine attack.