Background and study aim: Microscopic colitis is an increasingly recognized cause of chronic watery non bloody diarrhea. The diagnosis of microscopic colitis is mainly based on pathological examination of colonic biopsy from patients with chronic diarrhea and apparently normal colonoscopy examination. This study aimed at estimating frequency of microscopic colitis among patients with chronic watery non-bloody diarrhea and determining the role of some risk factors for its occurrence. Patients and Methods: This study included 60 patients with chronic watery non-bloody diarrhea. Colonoscopy examination was done for all patients and biopsy was taken for histopathology. All patients also evaluated by stool analysis, complete blood count, liver functions, kidney functions, thyroid functions, glycosylated hemoglobin, tissue transglutaminase and pelviabdominal ultrasound. Results: Microscopic colitis was diagnosed in 13 patients with 9 patients having lymphocytic colitis and 4 patients having collagenous colitis. The mean age of patients diagnosed with MC was about 45.7 ± 7.78 years and most of them were females (69.2 %). Patients with microscopic colitis suffered from diarrhea for longer durations. Microscopic colitis was more significant in patients with history of proton pump inhibitors and non-steroidal anti-inflammatory drugs use. Conclusion: Prevalence of microscopic colitis among studied patients was about 21.7% (15% lymphocytic colitis and 6.7% collagenous colitis). microscopic colitis was more common among females .