Considerable advances in the diagnosis and treatment of migraine headache have occurred during the past decade, but treatment options for acute migraine attacks have expanded at a faster rate than those for prophylaxis. We describe a patient whose migraine headaches responded dramatically to sustained-release niacin as preventive treatment. Niacin is not generally considered to be effective for migraine prevention. However, low plasma levels of serotonin have been implicated in migraine pathogenesis, and niacin may act as a negative feedback regulator on the kynurenine pathway to shunt tryptophan into the serotonin pathway, thus increasing plasma serotonin levels. Sustained-release niacin merits further study as a potentially useful preventive therapy for migraine headache.