Background/aims: The purpose of this study was to determine the frequency of defecation, gastrointestinal (GI) and non-GI symptoms among women with ulcerative colitis (UC) (n=38) and Crohn's disease (CD) (n=21), and to compare the results with those from healthy women (n=38) across the menstrual cycle. Methods: Women were followed for three menstrual cycles with a symptom diary consisting of frequency of defecation, and GI and non-GI symptoms. One point was allowed for each symptom in the same phases of three cycles, and total scores for GI and non-GI symptoms were obtained. Results: Frequency of defecation was found to be higher during menstruation in controls and in remitting UC and CD. GI symptom scores were higher in all three phases in patients with CD. These decreased in the postmenstrual phase in controls, and in patients with UC and remitting CD. In all three cycles, non-GI symptom scores were higher in patients with CD. These symptoms decreased during the postmenstrual period in all three groups. The activation of UC and CD did not affect the non-GI symptom score in the same menstrual cycle. Patients on mesalamine had less GI and non-GI complaints than those on sulfasalazine in all phases. There was no correlation between GI and non-GI symptom scores during all menstrual phases. Conclusion: Cyclic pattern present in healthy women persisted in patients with UC and CD. Disease activity and the drug used may modify the severity of the symptoms.