This study examined the effect of hormonal fluctuations on women's performance on sexually dimorphic cognitive tasks. Thirty-six participants were recruited through introduction to psychology courses at three colleges. Participants were assessed using the Woodcock-Johnson Test of Cognitive Ability III (WJ III COG), which is a commonly-used, widely accepted measure of cognitive ability, yet not previously used to evaluate women's cognitive ability in regard to hormonal fluctuations. In this study, participants' cognitive ability was assessed using two split-half forms of six subtests (four which have been found to be sexually dimorphic; two which were not found to be sexually dimorphic in regard to this particular evaluation, but have on other cognitive evaluations). Participants were assessed once during their predicted menses phase and once during their predicted ovulation phase. Raw scores and rates of the subtests between the phases were compared. Results indicated that there were no significant differences on sexually dimorphic tasks between phases of the menstrual cycle. Although in this study cognitive ability remained consistent throughout the menstrual cycle, further research must be conducted before it can be concluded that sex hormones do not affect cognitive functioning. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]