OBJECTIVES: Determine prevalence of employees (via self-report) experiencing migraine (MID) and non-migraine (NMIG) headaches; and extent of reduced productivity (absenteeism and presenteeism) in MIG and NMIG groups. METHODS: A total of 712 Health Risk Assessments were distributed to health care workers in a large, multispecialty medical group in Southern California; 455 returned (64% response rate). Respondents were 87% female; mean age of 45. Responders classified into no headache, migraine (defined by severity and frequency of symptoms using IHS criteria), and non-migraine. Headache sufferers were asked about absenteeism (full and partial days missed due to headache) and presenteeism (days worked with headache and self-reported productivity with headache) over the most recent 4 week period. RESULTS: Twenty-five percent reported having no headaches in past 6 months, 35% had non-migraine headaches, and 40% had migraines. Combining absenteeism and presenteeism, 68.3% MIG and 44.7% NMIG sufferers reported productivity loss due to headaches in the prior 4 week period. MIG sufferers reported a mean of 9.72 hours of lost productivity, of which 8.13 hours were due to presenteeism. NMIG employees reported a mean of 3.94 hours of lost productivity, of which 3.37 were due to presenteeism. On annualized basis, employees with migraines lost total of 15.85 days: 13.21 days due to presenteeism, 1.78 days due to full missed work days and 0.86 days due to partial missed days. The annual cost to the medical group for lost productivity for headache employees is $887,976 ($1247 per employee): $645,161 for MIG sufferers and $229,815 for NMIG employees. CONCLUSIONS: The results of this employee survey demonstrate that migraine headaches are both a prevalent and expensive condition for an employer. The magnitude of the cost is surprisingly large in a health care organization with employees who would be assumed to be fairly sophisticated and have ready access to physicians for diagnosis and treatment.