We examine the theoretical basis of screening, followed by an evaluation of screening initiatives from a population health perspective and a discussion of the organisation of mass screening programmes. Evidence for the effectiveness of screening by primary site from both randomised trials and evaluation of service screening is summarised and the existing cancer screening programmes in the European Union are described. Sufficient evidence from several randomised trials to demonstrate mortality reduction exists for breast cancer and colorectal cancer screening. At least one trial has shown efficacy with a mortality end-point in screening for hepatocellular carcinoma and oral cancer. Randomised trials have demonstrated a lack of mortality effect in lung cancer screening based on chest X-ray and sputum cytology. Despite the lack of randomised trials, population screening for cervical cancer with cytological smears has been convincingly shown to reduce cervical cancer incidence and mortality.