The circadian system with its centre in the hypothalamus is involved in migraine pathophysiology. Whether it plays a pivotal role is not clarified. The investigators postulate that a destabilized circadian system may increase migraine attack susceptibility, and that stabilization by supplying melatonin a migraine preventive effect will be achieved.

A previous open label study has shown effects that certainly warrant a placebo controlled study.

Inclusion Criteria:

• Patients between 18 and 65 years, both male and females.
• Migraine present for at least 1 year and fulfilling diagnostic criteria that conform to those of the International Headache Society (HIS) [2] but otherwise healthy.
• Attacks of migraine should occur 4-6 times per month, there should be no regular use of other drugs, and the patient has to be able to differentiate between migraine headache and non-migrainous headache.
• Preventive drugs for migraine should not have been used the last three months.
• Conventional acute attack treatment is accepted, but not sporadic use of other drugs like hypnotics and anxiolytics.
• Residence of North-Norway.

Exclusion Criteria:

• Medication overuse headache, chronic migraine.
• Pregnant and breast feeding women.
• Patient with either serious co-morbidity or conditions requiring medical treatment or caution.
• Psychiatric disease.