Irritable bowel syndrome and functional bowel disorder are diagnoses used to describe chronic GI symptoms for which no overt pathological condition can be identified. Symptoms are more common in women and are frequently followed in gastroenterology clinics. The purpose of this article is to provide an overview of the research linking GI symptoms and reproductive cycling and to discuss implications for practice. GIGl symptoms such as stomach pain and nausea are highest during menses compared with other cycle phases; also, stool consistency is loosest at menses. This pattern is present in control subjects. In women with irritable bowel syndrome the same pattern is seen but with higher symptom intensity. Although animal studies have demonstrated that estrogen and progesterone modulate contractile function of some GI segments. In humans, symptoms are highest when these hormones are at the lowest levels. Thus, symptoms in women may be related to decreasing ovarian hormone levels or to other circulating hormones or factors which vary with the menstrual cycle. Additionally, other factors such as stress aggravate symptoms. Therapeutics directed toward increasing patient awareness of cyclic patterns in symptom complaints, for example, via the use of daily symptom diaries may be a useful adjunct to dietary, pharmacological, and other therapies.