• Division of Cancer Prevention and Control, National Cancer Institute, Bethesda, Maryland 20892.

Frequently, the medical and lay community has assumed that earlier diagnosis of cancer of any type automatically confers benefit and that any diagnostic test that can identify early stages of disease must therefore be useful for screening. However, there is an emerging science of screening which affords a more rigorous approach to public health recommendations in the application of new technologies to screening and early detection. A number of public health groups and agencies are using an evidence-based approach in making recommendations. Using this approach, early detection methods for ovarian cancer would meet only the weakest level of evidence to support their routine application in asymptomatic women. For this reason, the National Cancer Institute has recently launched a large randomized clinical trial to test the effectiveness of screening for ovarian cancer.