 Single flexible sigmoidoscopy FS, between the ages of 55 and 65 years, has been shown to bring about a significant reduction in colorectal cancer mortality. In addition, and most importantly, after a period of four years a significant reduction in colorectal cancer incidence was observed. FS does not suffer from low specificity since false positives do not occur, and there is independent evidence that it is more sensitive than a single gFOBT. In addition, FS is ideally suited to detecting rectal cancers and adenomas, and it is unlikely that there would be a gender difference in the sensitivity. 