Microscopic colitis (MC) is viewed as an umbrella term applicable to both lymphocytic and collagenous colitis. The first case was published in 1976, a new entity with chronic watery diarrhea with lymphocytic colitis, with or without a subepithelial collagen deposition. Patients are usually middle-aged women, and the pathogenesis is unknown. The response to steroids and the female predominance underlines an autoimmune disease. Up to 40% NSAID's and Lanzoprazole-induced MC are well-known. Biopsies during sigmoidoscopy in unexplained diarrhea must be standard. Treatment is empirical. The most important step is to ban all NSAID's and other MC inducing agents. Immunosuppressive treatment must be considered. However the disease has a benign course and sometimes is selflimiting.