Premenstrual syndrome is a term which is used for describing of somatic, cognitive, emotional, and behavioral symptoms that occur during the luteal phase of menstrual cycle in women of reproductive age; symptoms rapidly improve at the onset of menstruation. In this study, we aimed to reveal if cognitive functions are affected or not in PMS and if the subjects are affected, we try to explain this situation by an objective diagnostic test. Ethical committee approval was taken for this project on 09.03.2012 and numbered 050.99-60. In this study, in order to determine premenstrual syndrome, “Premenstrual Syndrome Scale” that is developed by Gençdoğan (2006) with 44 items, Likert type, and 9 subgroups was used. Sample size was calculated using simple random sampling with a confidence level of 95% and confidence interval of 0.05. A total of 60 participants were included in the study (calculated sample size was 30 for each group). Each group was recorded in the ENMG-UP laboratory using the OIP auditory warning and the “oddball two-tone discrimination task” method. Latency measurements were taken from the highest point of the peak, and amplitude measurements were taken from peak to peak with a cursor. Comparisons of P300 wave latencies obtained via sparse auditory stimulus in PMS and non-PMS groups were made and findings were summarized in one of the tables. Recordings are taken from three scalp regions: parietal and central, respectively. PMS women have longer P300 wave latencies in all regions compared to non-PMS group, whereas there is no significant difference between P300 amplitude.