Chronic headache sufferers represent a diverse population which is difficult to study. Population-based studies suggest that many headache sufferers do not seek medical care for their headaches and do not use prescription drugs to treat them. Studies conducted among headache patients in clinical settings suggest that these patients have more severe headache symptoms, use more prescriptions drugs, and are heavier users of medical resources. Data from both types of studies must be considered if the comprehensive cost of chronic headache is to be estimated.