During women's reproductive years, migraine is three times more common than in men of a similar age. Although this female preponderance is commonly assumed to be associated with the additional trigger of fluctuating sex hormones of the menstrual cycle, few studies have been done to confirm or refute this. This review is confined to the relation between oestrogen and attacks of migraine. The evidence for an association between oestrogen "withdrawal" and attacks of migraine without aura is presented, as well as evidence for an association between high oestrogen states and attacks of migraine with aura. Only clinical data are presented here.