The sensitivity, specificity and positive predictive value of fecal blood testing are too poor to allow its general use as a screening test for colorectal cancers. Even the predictable qualitative improvement of these tests will be of no avail with regard to non-tumoral sources of bleeding or the non-hemorrhagic tumoral sources of bleeding or the non-hemorrhagic tumours which are frequent in the early stages of colorectal cancer. It is therefore essential to define high-risk groups, to pay particular attention even to minor symptoms, and to perform the necessary endoscopic or radiological diagnostic tests.