Microscopic colitis is a common cause of chronic diarrhoea, particularly in the elderly. The colonic mucosa appears normal or nearly normal at endoscopy, and the diagnosis is made on histologic grounds in the appropriate clinical setting. There are 2 subtypes, collagenous and lymphocytic colitis, that are clinically and histologically similar, but which can be differentiated by the presence or absence of a thickened subepithelial collagen band. The entity of drug-induced microscopic colitis and/or concomitant celiac sprue needs to be considered when evaluating these patients. There are few controlled treatment trials in microscopic colitis, with budesonide being the best studied drug. Despite this fact, systematic approach to therapy often leads to satisfactory control of symptoms.