Flexible sigmoidoscopy is a faster procedure compared to colonoscopy. It does not require sedation and the person can return to work soon after the procedure. In contrast, colonoscopy takes longer time and requires sedation. However, colonoscopy permits examination of the entire colon whereas in sigmoidoscopy, only the last part of the colon is examined. Thus a number of cancers especially those on the right side could be missed in flexible sigmoidoscopy. Flexible sigmoidoscopy should be repeated every 5 years whereas colonoscopy every 10 years.