This study examined the relationship between migraine, chest pain, and risk of myocardial infarction (MI) in a retrospective cohort of 79,588 enrollees in the northern California Kaiser Permanente Medical Care Program who underwent comprehensive, multiphasic preventive medicine examinations in 1971 to 1973. Migraine was ascertained by questionnaire as either symptom-based or self-report of physician diagnosis. Chest pain was ascertained by two questions regarding feelings of pain, pressure, or tightness in the chest that either hurt in the middle under the breastbone or forced the respondent to stop walking. Follow-up began at the time of each participant's medical examination and continued until the earliest occurrence of hospitalization for MI, death, termination of enrollment, or December 1987. There was a strong relationship between migraine and chest pain, but, in general, no significant association was found between migraine and risk of MI except among women with a family history of MI in whom a self-reported physician diagnosis of migraine was related to a greater than two-fold increase in risk.