The many unique structural and functional features of the intestine may offer explanations to the well-established association between arthritis and inflammatory bowel diseases (IBD). In ulcerative colitis (UC) and Crohn's disease (CD) some 6-8% of cases develop peripheral joint disease which frequently correlates with the activity and extent of the underlying bowel disorder. Ankylosing spondylitis is also found rather frequently in UC and CD, but is apparently not related to the severity of colitis. The occurrence of rheumatic manifestations in these two IBD is reviewed in detail.