Screening people for serious diseases is receiving increasing attention as studies demonstrates the potential benefits of early detection and early intervention in preventing morbidity and mortality. Screening tests are available for some of the most important noncommunicable diseases, including cardiovascular disease, type 2 diabetes and several site-specific cancers. However, screening guidelines for cardiovascular disease, cancers and diabetes vary within and between countries because many national and international organizations are developing their own guidelines. There is a need to address the issue of screening for disease, with an emphasis on providing accurate and practical information relevant to all countries. This report arose from a Consultation Group meeting held at WHO headquarters in Geneva. It presents an examination of the principles of screening with an emphasis on noncommunicable disease prevention and control policy.