This article reviews the substantial impact of migraine on individual headache sufferers and on society. While the individual impact of migraine is determined by pain and role dysfunction, the societal impact is primarily determined by work loss and disability in the work place and at home. Epidemiologic studies demonstrate that migraine is very common, substantially under diagnosed and often inadequately treated. Improving health care delivery to persons with migraine could substantially reduce the individual and societal impact of the illness. Migraine ranges in severity, with mild headache and no disability on one extreme and excruciating pain and complete disability on the other. Because of this spectrum of severity, diagnosis alone does not provide enough information to permit the selection of optimal therapy. A headache grading system might help headache sufferers and clinicians match the therapy not only to the diagnosis but to the overall severity of illness; such a system provides the best hope for cost effective health care interventions.