Women often report worsening of their seizures in association with menstrual cycles. If seizure frequency consistently doubles or more in association with a phase of the menstrual cycle, then the woman is defined as having “catamenial epilepsy.” How often this occurs has been studied by several researchers in the past, including Andrew Herzog Mark Yerby, Martha Morrell, Page Pennell, Cynthia Harden, J.I. Isojarvi, Nancy Foldvary-Schaefer, Mark Quigg and others. Now a group from the Republic of Korea (Kim and colleagues, Epilepsy Research, 2010, volume 90, pages 214-220) has prospectively quantified seizure frequency in association with 255 menstrual cycles in 79 women with epilepsy. Overall, 46.8% of women had increased seizures either during the menstrual cycle or the ovulatory phase mid-way between menstrual cycles. Seizures also were common during anovulatory cycles, which is a menstrual cycle without secreting an ova. Seizure frequency tended to be lowest during the mid-luteal phase after ovulation, when progesterone hormone levels are high. These observations offer support for continuing to search for hormonal therapies that might be helpful for seizure control in women with catamenial epilepsy.