There was no group difference in reaction times and accuracy between males and females (using contraception and not). However, within subject analyses revealed that regularly menstruating females performed better during menstruation compared to being in any other phase, with faster reaction times (10ms c.ca, p < .01), fewer errors (p < .05) and lower dispersion intra-individual variability (p < .05). In contrast they exhibited slower reaction times (10ms c.ca, p < .01) and poorer timing anticipation (p < .01) in the luteal phase, and more errors in the predicted ovulatory phase (p < .01). Self-reported mood, cognitive and physical symptoms were all worst during menstruation (p < .01), and a significant proportion of females felt that their symptoms were negatively affecting their cognitive performance during menstruation on testing day, which was incongruent with their actual performance.