The MIDAS Questionnaire was developed to assess headache-related disability with the aim of improving migraine care. Headache sufferers answer five questions, scoring the number of days, in the past 3 months, of activity limitations due to migraine. The internal consistency, test-retest reliability, and validity (accuracy) of the questionnaire were assessed in separate population-based studies of migraine sufferers. In addition, the face validity, ease of use, and clinical utility of the questionnaire were evaluated in a group of 49 physicians who independently rated disease severity and need for care in a diverse sample of migraine case histories. The test-retest Pearson correlation coefficient for the total MIDAS score was approximately 0.8. The MIDAS score was valid when compared with a reference diary-based measure of disability; the overall correlation between MIDAS and the diary-based measure was 0.63. The MIDAS score was also correlated with physicians' assessments of need for medical care (r = 0.69). From studies completed to date, the MIDAS Questionnaire has been shown to be internally consistent, highly reliable, valid, and correlates with physicians' clinical judgment. These features support its suitability for use in clinical practice. Use of the MIDAS Questionnaire may improve physician-patient communication about headache-related disability and may favorably influence health-care delivery for migraine patients.