The prospects for mass population screening in colorectal cancer.

Screening leads to an increased detection of tumours localized to the bowel at the time of surgical treatment which are likely to have an improved prognosis. However, because of the biases associated with screening it would be unwise to advocate a nationwide programme until the results of the controlled trials now in progress are available. At the present time the detection of occult blood in the faeces is the only feasible method of population screening. Haemoccult is a reliable, well tried test but lacks sensitivity. Several new chemical and immunological tests are available but require further evaluation.