Background/Aims: The aim of this retrospective survey is to determine the frequency of collagenous colitis among patients who presented with chronic diarrhea to our gastroenterology outpatient clinic and to evaluate the demographic, clinical and laboratory findings of these patients and the treatment modalities. Methodology: We reviewed the charts of the patients who had presented with chronic diarrhea to our outpatient clinic during four years. We identified the patients who were diagnosed to have collagenous colitis on histopathological examination. Results: Among the 93 patients who presented with chronic diarrhea, 7 (7.5%) were diagnosed as collagenous colitis. Six of these patients were female, the mean age was 64 +/- 11.5 years. Celiac disease was diagnosed in 2 of these patients. Laboratory examination showed anemia in 2 patients, hypoalbuminemia in 4 patients and high C-reactive protein levels in 3 patients. Five patients, were treated with mesalazine, 1 patient with salazopyrine and 1 with methylprednisolone. Remission was obtained in all of these patients except for one; in this case budesonide was started instead of mesalazine. Conclusions: Collagenous colitis was detected in 7.5% of the patients who presented with chronic diarrhea to our gastroenterology outpatient clinic. They were usually middle aged female patients. Mesalazine was effective in most of these patients.