Migraine is a leading cause of disability worldwide; approximately half of those affected have such severe attacks that they cannot function normally in routine daily activities. Research is beginning to focus upon the burden of migraine between attacks, referred to as interictal burden. This burden encompasses worry and expectation of future attacks that consequently may be associated with limitations in social and family interactions, as well as work capacity. This review aims to increase physician awareness of the degree and scope of functional impairment associated with migraine. Physicians are in a position to assess the true impact of migraine in their patients using techniques such as open-ended questions during visits, and paper-based migraine assessment tools such as the Migraine Disability Assessment questionnaire. Eliciting such information on interictal burden may help the physician prescribe the most appropriate therapy based on their patients' degree of impairment. This article also describes the instruments most widely used for measuring migraine-related functional impairment, summarizes studies assessing the effects of migraine on indicators of health-related quality of life and presents data on how preventive migraine treatment may beneficially influence migraine-related functional impairment.