OBJECTIVE: To determine the prevalence of complementary and alternative medicine (CAM) use over time in a population-based cohort of patients with inflammatory bowel disease (IBD). METHODS: The Manitoba IBD Cohort Study is a longitudinal, population-based study of multiple determinants of health outcomes in an IBD cohort. Participants completed semi-annual surveys, and annual in-person interviews. Enquiries about the use of 12 types of CAM service providers and 13 CAM products, based on items from a national survey, were included at months 0, 12, 30 and 54. RESULTS: Overall, 74% of respondents used a CAM service or product in the 4.5-year period, with approximately 40% using some type of CAM at each time point, and 14% using CAM consistently at every time point. There was a trend for women to use CAM more than men; there was no difference in CAM use between patients with Crohn's disease and those with ulcerative colitis. The most often used CAM services (on average) were massage therapy (30%) and chiropractic (14%), physiotherapy (4%), acupuncture (3.5%) and naturopathy/homeopathy (3.5%). A wide range of CAM products were used, with Lactobacillus acidophilus (8%), fish and other oils (5.5%), glucosamine (4%) and chamomile (3.5%) as the most common. On average, only 18% of consumers used CAM for their IBD, so the majority chose it for other problems. There were no differences in psychological variables between CAM users and non-users. CONCLUSIONS: Those with IBD commonly try CAM, although very few use these approaches regularly over the years. CAM is not usually used by patients with IBD for disease management, but clinicians should be aware that many will test the services and products.