Microscopic colitis (MC) is a cause of chronic diarrhea, and there are 2 subtypes: collagenous colitis (CC) and lymphocytic colitis (LC). The clinical features, symptoms, and responses to treatment are similar for both CC and LC. All meta-analyses conducted for this technical review tested for interaction (or a subgroup effect), and in every case there was no evidence of a subgroup effect. Therefore, in this review, the 2 subtypes are combined and considered together as MC. Information on pathophysiology was considered outside the scope of this review.