BACKGROUND We wanted to evaluate the aetiology, age incidence, histopathology, site of occurrence of lower gastrointestinal bleeding using colonoscope. We also wanted to study the clinical presentations of different types of lower gastrointestinal bleeding along with effect of diet on it. MATERIALS AND METHODS 134 patients were selected for the study who had complained of per rectal bleeding. After bowel preparation using colonoscope Olympus CV-170, both macroscopic & histopathological diagnosis, most common site involved and age of incidence were determined. RESULTS This study of 134 cases shows that the mean age of diagnosis was 44.40 years. For all types of lower gastrointestinal bleeding, the age range was (2-83) years. The most common aetiology of lower gastrointestinal bleeding is internal haemorrhoids-45 (33.58%), followed by normal mucosa in 33 (24.62%) cases and the least common is lax anal canal with posterior anal fissure 1 case (0.74%). Colorectal masses, inflammatory and/or ulcerative colonic lesions & polyps were found in 15 (11.19%), 18 (13.43%) and 13 (9.70%) cases respectively. 15 (11.19%) cases had colorectal cancer. Male 8 (5.97%) cases have higher percentage of cancer than female 7 (5.22%) cases. Mean age of diagnosis of colorectal cancer in this series is 45.13±18.05 years. Rectum (58.20%) is the most common site involved followed by whole colon (24.62%). The study carried out had bleeding per rectum (100%) & constipation (100%) in all patients. Dehydration (11.19%) and anorexia (11.19%) were the least common clinical presentations. Biopsy was done in 27 (20.14%) cases, which revealed adenocarcinoma in 14 (10.44%) cases followed by mucinous adenocarcinoma in 1 (0.74%) case. Rectal polyps were found in 12 (8.95%) cases. Dietary habit has definitive role as shown by non-vegetarian/vegetarian ratio 5.06. Only 54 (40.44%) cases had definite family history. Rectal polyps in this set up were more commonly seen in younger age (22.23 ± 20.63 years) group, in whom histopathological evaluation was done to rule out future possibility of malignancy. In many cases of colonoscopy, no abnormality was detected. The most common aetiology of lower gastrointestinal bleeding in these cases was irritable bowel syndrome which was further evaluated by esophago-dudenoscopy and enteroscopy. CONCLUSION Colonoscopy is one of the best modalities to diagnose causes of lower gastrointestinal bleeding. It will be better to have screening colonoscopy after age of 50.