The aim of this study was to analyze the gynecological and hormonal condition of five patients with catamenial epilepsy and to establish a relationship with the presence of convulsive crises. The clinical profiles of five patients were obtained and their serum levels of anticonvulsants and sex steroids were determined. Four patients showed obvious signs of premenstrual tension syndrome (PMTS), with retention of fluid and reduction of the serum levels of anticonvulsants, which were restored to therapeutic levels after treatment of the PMTS. The fifth patient presented with chronic anovulation, which was treated by administration of progesterone during the second phase of the menstrual cycle, resulting in an improvement in the frequency of convulsions. In the cases studied, the low levels of progesterone and their rapid fall in PMTS, as well as the raised levels of circulatory estrogens in the anovulatory menstrual cycle, appear to be implicated in the convulsive disorder of catamenial epilepsy.