Almotriptan malate, and several other treatments for migraine headaches, known as triptans, are approved for the treatment of migraine headaches in adults. To date, none of these have been approved by the Food and Drug Administration (FDA) for use in adolescents. This is an open-label, multi-center study that will enroll approximately 450 patients aged 12 - 17 years old with a history of one to 14 migraines per month for the 6 months prior to entering the study. The total study duration will be up to one year. There is a screening phase to determine if the patient is eligible for study entry, followed by an open-label treatment phase that can last up to one year. Almotriptan malate 12.5 mg tablets will be used to treat all migraine headaches during the study, as needed. The primary outcome of the study is an assessment of the long-term safety of almotriptan malate in adolescent migraine sufferers. The study hypothesis is that the almotriptan malate will be safe and well tolerated in the treatment of adolescent migraine headaches. Safety measurements will be performed at set time points during the study and will include laboratory tests, physical and neurological exams, electrocardiograms (ECGs) and the incidence of adverse events. A diary will be completed by the patient for each migraine headache for which they take almotriptan malate. Migraine pain information and almotriptan malate use will be recorded in the headache diary. An equal number of patients in the 12 - 14 year old range as the 15 - 17 year old range will be enrolled. Patients will take one 12.5 mg almotriptan malate tablet by mouth after the onset of migraine headache pain. The dose may be repeated once if the pain continues 2 hours after the first dose, but no more than 2 doses can be taken within a 24-hour period. Study medication will be taken for up to one year.