Sixty percent of women who experience migraine headaches self report that the headaches worsen with their menstrual period. The current literature suggests these headaches may be related to rapidly falling estrogen levels on migraine headaches outside of the perimenstrual period. The specific aims of this study are as follows: 1) To evaluate the effect of hormone fluctuations on the severity and disability of migraine headaches. 2) To determine the impact of pharmacologically reducing hormonal fluctuations, using a GnRH agonist, on headache severity and disability. 3) To evaluate if adding constant doses of estrogen to women on a GnRH agonist decreases headache severity and disability. 4) To compare if there is a difference in headache severity and disability in women treated with GnRH alone compared to those treated with GnRH and the estogen therapy. 5) To evaluate cerebral blood flow velocities (BFV's) and CO2 cerebrovascular reactivity (CVR) using transcranial Doppler studies (TCD) in female migraineurs at different phases of the menstrual cycle. 6) To study the effect of hormonal manipulation (GnRH/placebo and GnRH/estrogen groups) on BVF's and CVR as compared to baseline measures.