A review of the literature suggested that falling levels of estrogen may trigger headaches for many women. A double blind controlled cross-over study was carried out on 49 women, all of whom had undergone a surgical menopause. During the study each woman was randomly allocated each of the following drugs daily for three months: ethinyl estradiol 50 μg; d norgestrel 250 μg; combination of ethinyl estradiol 50 μg and d norgestrel 250 μg; and placebo. Women who reported they were headache free sufferers in the past had higher neuroticism and lower extraversion scores than others. Women who suffered headaches during a hormone free time interval had significantly higher plasma testosterone levels. An increase in the frequency of headaches occurred in association with a fall in estrogen content of the medication.