This overview of the published epidemiological evidence of migraine helps to identify the size of the public-health problem that migraine represents. It also highlights the need for further epidemiological studies in many parts of the world to gain full understanding of the scale of clinical, economic and humanistic burdens attributable to it. This paper presents some of the work on migraine undertaken by the World Health Organization (WHO) in the Global Burden of Disease study conducted in 2000 and reported in the World Health Report 2001. Migraine was not included in the first Global Burden of Disease 1990. The paper also discussed the measurement of disability attributable to headache disorders using WHO ICF Classification. Using disability-adjusted life years (DALYs) as a summary measure of population health (which adds disability to mortality), WHO have shown that mental and neurological disorders collectively account for 30.8% of all years of healthy life lost to disability (YLDs) whilst migraine, one amongst these, alone accounts for 1.4% and is in the top 20 causes of disability worldwide. This information is combined with the increasingly widely accepted belief that disability and functioning are relevant parameters for monitoring the health of nations and that there is an increasing need to measure them. WHO's Classification of Functioning, Disability and Health (ICF) provides a model of human functioning and disability, as well as a classification system, that allows us to highlight and measure all dimensions of disability. ICF applied to headache disorders allows comparability with other health conditions as well as evaluation of the role of the environment as a cause of disability amongst people with headache. Migraine causes a large proportion of the non-fatal disease-related burden worldwide. Our knowledge of headache related burden is incomplete and it is necessary to add to it epidemiological studies in many parts of the world and to combine this with measurements of disability using both DALYs and WHO's ICF Classification. The work described here has been the base for the Global Campaign against Headache disorders: "Lifting the Burden", launched in 2004 jointly by WHO, IHS (International Headache Society), WHA (World Headache Alliance) and EHF (European Headache Federation).