 In a recent randomised trial carried out in 14 UK centres, a 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, presumably as a result of the routine removal of adenomas at FS. Interestingly, the reduction in incidence was restricted to left-sided cancers despite the fact that total colonoscopy was carried out in all those with a significant index lesion found at FS 5 of the screened population. 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 or FIT. 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. 