A detailed questionnaire concerning life history of headache and its characteristics was administered to 1,809 nonmedical volunteers. Questions dealt with severity of headache, the nature of preceding and accompanying phenomena (nausea, visual scotomata, neurologic symptoms), precipitating factors, and history of other illness. For the total sample and in the 25 to 39 age group, severe or disabling headaches were significantly more frequent in women and mild headaches were significantly more common in men. Migraine characteristics were common with mild headache. An association between hypertension and severe headache was found in women, between asthma and severe headache in men.