The P3 component of a visual event related potential (ERP) was studied for five consecutive weeks in six women with normal menstrual cycles. Serum concentrations of luteinizing hormone (LH), estradiol (E2) and progesterone were studied during the same period. Increases in P3 amplitude, although nonsignificant, were noted in the week preceding onset of menses. No significant changes in reaction times to target/nontarget stimuli were noted over the same time period.