Earlier studies investigating the effects of premenstrual syndrome (PMS) on cognitive functioning have generally suggested that there is no substantial relationship between the premenstrual phase and cognitive functioning. Despite these findings, however, many women with PMS continue to self-report changes in cognitive performance. Discussions regarding this discrepancy tend to support the notion that perceived changes in cognitive performance associated with the premenstrual phase may be influenced by expectations induced by the media, etc. This study attempted to further explore the effects of PMS on cognitive functioning and examine the contributions of biases or expectations on the inconsistency of self-report versus actual changes in cognitive performance associated with the menstrual phase for PMS females;Forty females, selected on the basis of their responses to a retrospective questionnaire and three months of daily ratings, were divided into two groups--Group I was tested first during the luteal phase and Group II was tested first during the intermenstrual phase. Subjects individually completed cognitive tasks intended to assess attention, memory, and concentration during the luteal and intermenstrual phase of their cycles. In addition, subjects returned and were given one of two expectional sets, based on bogus previous findings, prior to the final luteal phase testing;Results from this study revealed distinct phase-related changes only for recognition memory. Additional phase-related cognitive changes, however, were observed following phase by order analyses and suggested that (1) subjects initially tested during the luteal phase were disadvantaged in their ability to perform such tasks, and (2) women in the luteal phase of their cycle failed to improve from previous exposure or practice on the tasks. Finally, results from the instructional manipulation demonstrated that only reaction time, versus performance accuracy, was affected due to expectations. The results of the study are discussed at length with respect to contributing factors and implications for continued research in this area.