This study evaluated the validity of family history data on severe headache and migraine obtained from adult probands with epilepsy in a family study of seizure disorders. We compared the probands' reports of severe headaches and migraines in their parents and full siblings with symptom-based diagnoses based on self-reports. Overall sensitivity was 48% for severe headache and 44% for migraine. When we used reports of severe headaches to screen for migraine headaches in the relatives, sensitivity was 56%. These results indicate that severe headache and migraine are underreported in family history interviews with first-degree relatives. To obtain accurate information on headaches in families for clinical practice and genetic research, direct interviews with each relative may be required.