Cytomegalovirus (CMV) colitis is rarely reported in the immuno-competent adult and is often associated with inflammatory bowel disease (IBD), particularly ulcerative colitis (UC).  An index of suspicion in the appropriate setting is vital to diagnosing the condition. Undiagnosed CMV colitis has a significant morbidity.  A review of the natural history and diagnosis of CMV is followed by a discussion of the incidence, outcome and possible treatment of CMV in the immunocompetent patient. The possible association between CMV and IBD is also reviewed, and the question of whether this should have any bearing on treatment is discussed at some length.