Colonoscopy is a valuable tool for diagnosis and treatment of many diseases of the large intestine. Abnormalities suspected by X-ray can be confirmed and studied in detail. Even when X-rays are negative, the cause of symptoms such as rectal bleeding or change in bowel habits may be found by colonoscopy. It is useful in the diagnosis and follow-up of patients with inflammatory bowel disease as well. Colonoscopy’s greatest impact is probably in its contribution to the control of colon cancer by polyp removal. Before colonoscopy became available, major abdominal surgery was the only way to remove colon polyps to determine if they were benign (non-cancerous) or malignant (cancerous). Now polyps can be removed easily and safely without surgery. Periodic colonoscopy is a valuable tool for follow-up of patients with previous polyps, colon cancer or a family history of colon cancer. Colonoscopy is a safe and extremely worthwhile procedure, which is very well tolerated. There is still a chance that a polyp behind a fold could be missed. If you have questions, do not hesitate to speak to your doctor about it.