Migraine headache is responsible for significantly more healthcare resource and lost labour costs than previously reported. Costs associated with migraine were assessed via a survey conducted in 940 patients, 70% of whom responded. All met the International Headache Society's diagnostic criteria for migraine and had participated in one of two multicentre, single-dose, parallel-group, randomised, placebo-controlled clinical trials designed to assess the efficacy of an anti-migraine compound. Migraine frequency and costs, in terms of healthcare resource utilisation and lost labour (decreased productivity and missed workdays), were assessed. Over 90% of respondents visited a clinic and nearly 50% presented to an emergency room for treatment of migraine-related symptoms at least once in the year prior to the survey. These 648 respondents used an estimated $US529 199 per year in healthcare services. 89% of employed respondents reported that job performance was adversely affected by migraine and over 50% of them missed at least two days of work per month. Depending on the estimates used for migraine prevalence and using 1986 estimates of median earnings for the US work force, the extrapolated costs to employers ranged from $US5.6 billion to $US17.2 billion dollars annually due to decreased productivity and missed work days. The cost of migraine is not fully appreciated by the medical community or by society.