---

Introduction: Chronic diarrhea is accomp-anied with abdominal symptoms and restr-icts the activity of patient. Precise evaluat-ion of the history of patient, physical exam-ination, laboratory and radiological evalu-ation, colonoscopy and biopsy may be help-ful to determine the underlying causes of chronic diarrhea. Materials & Methods: For the study, 100 patients (50 male and 50 female) with chro-nic diarrhea were studied. These patients had referred to Tabriz Sina hospital, Iran during 2006 to 2011. The patients were examined for the presence of fecal leuko-cytes, parasitic eggs and trophozoites. Stu-dding parameters such as colonoscopic fin-dings and final diagnoses based on intes-tinal mucous biopsy were study. Data were analyzed by using of SPSS software and the statistical tests, frequency and chi-square. Findings: Mean age of men was 36.44 year and men age of women was 38.56 year. Colonoscopic findings were as 61% infla-mmation, 10% erosion and 29% normal. Biopsy study findings were as 59% nonsp-ecific colitis, 15% ulcerative colitis and 26% amebic colitis. Discussion & Conclusion: Chronic diarrhea may be only one symptom of underlying di-gestive diseases. Therefore, after exclusion of infective and parasitological causes, inv-asive diagnostic method is indicated. The two method are together considered useful diagnostic tool for the management of the chronic disease and prevent the undesired economical and health problems for the patients.