OBJECTIVES: Shift work has been associated with gastrointestinal symptoms such as abdominal pain, constipation, and diarrhea. These symptoms overlap with those reported by patients with functional bowel disorders. Because shift work will lead to misalignment between the endogenous circadian timing system and the external 24 h environment, we hypothesized that nurses participating in shift work will have a higher prevalence of functional bowel disorders when compared with nurses participating in day shifts. METHODS: Nurses engaged in patient care were invited to complete Rome III, irritable bowel syndrome-quality of life measure (IBS-QOL) and modified Sleep-50 questionnaires. Respondents were classified as working day, night, or rotating shifts. The prevalence of IBS, functional constipation, functional diarrhea, and individual gastrointestinal symptoms was determined. RESULTS: Data were available for 399 nurses (214 day shift, 110 night shift, and 75 rotating shift workers). Rotating shift nurses had a significantly higher prevalence of IBS compared to day shift nurses (48% vs. 31%, P<0.01). Multivariable logistic regression correcting for age, gender, and sleep quality proved this association robust. IBS-QOL scores among groups were similar. Prevalence of functional constipation and functional diarrhea was similar between groups. Rotating shift nurses had a significantly higher prevalence of abdominal pain compared to day shift (81% vs. 54%, P<0.0001) and night shift workers (61%, P=0.003). CONCLUSIONS: Participation in shift work, especially rotating shift work, is associated with the development of IBS and abdominal pain that is independent of sleep quality. Circadian rhythm disturbances may have a function in the pathogenesis of IBS and abdominal pain.