Chronic watery diarrhoea is the main symptom of the microscopic colitis syndrome, including collagenous colitis (CC), lymphocytic colitis (LC), and not otherwise specified (NOS) colitis. The goal of this study was to evaluate the anti-diarrhoeal effect of cholestyramine in non collagenous microscopic colitis. The records of 13 patients with LC and 7 patients with NOS, who had received cholestyramine as first line therapy and who responded to a questionnaire, were reviewed. On an intention to treat basis, a good clinical effect of cholestyramine was achieved in 75 % of the patients in both LC and NOS colitis. There was no therapeutic effect in 15 % of the patients, who all had LC. In general, the anti-diarrhoeal effect appeared within one week of treatment. Cholestyramine provides a rapid and adequate symptomatic relief of the diarrhoea in non collagenous microscopic colitis.