OBJECTIVE: To provide heatlh care providers, patients, and the general public with a responsible assessment of currently available data regarding the effectiveness of mammography screening for women ages 40-49. PARTICIPANTS: A non-Federal, nonadvocate, 12-member panel representing the fields of oncology, radiology, obstetrics and gynecology, geriatrics, public health, and epidemiology and including patient representatives. In addition, 32 experts in oncology, surgical oncology, radiology, public health, and epidemiology, presented data to the panel and to a conference audience of 1,100. EVIDENCE: The literature was searched through Medline and an extensive bibliography of references was provided to the panel and the conference audience. Experts prepared abstracts with relevant citations from the literature. Scientific evidence was given precedence over clinical anecdotal experience. CONSENSUS PROCESS: The panel, answering predefined questions, developed its conclusions based on the scientific evidence presented in open forum and the scientific literature. The panel composed a draft statement that was read in its entirety and circulated to the experts and the audience for comment. Thereafter, the panel resolved conflicting recommendations and released a revised draft statement at the end of the conference. The final statement with a minority report was completed within several weeks after the conference. CONCLUSIONS: The Panel concludes that the data currently available do not warrant a universal recommendation for mammography for all women in their forties. Each woman should decide for herself whether to undergo mammography. Her decision may be based not only on an objective analysis of the scientific evidence and consideration of her individual medical history, but also on how she perceives and weighs each potential risk and benefit, the values she places on each, and how she deals with uncertainty. However, it is not sufficient just to advise a woman to make her own decision about mammograms. Given both the importance and the complexity of the issues involved in assessing the evidence, a woman should have access to the best possible relevant information regarding both benefits and risks, presented in an understandable and usable form. Information should be developed for women in their forties regarding potential benefits and risks to be provided to enable each woman to make the most appropriate decision. In addition, educational material to accompany this information should be prepared that will lead women step by step through the process of using such information in the best possible way for reaching a decision. For women in their forties who choose to have mammography performed, the costs of the mammograms should be reimbursed by third-party payors or covered by health maintenance organizations so that financial impediments will not influence a woman's decision. Additionally, a woman's health care provider must be equipped with sufficient information to facilitate her decisionmaking process. Therefore, educational material for physicians should be developed to assist them in providing the guidance and support needed by the women in their care who are making difficult decisions regarding mammography. The two panel members writing a minority report believed the risks of mammography to be overemphasized by the majority and concluded that the data did support a recommendation for mammography screening for all women in this age group and that the survival benefit and diagnosis at an earlier stage outweigh the potential risks.