Public policy involving the lives of thousands of individuals and large resources should not normally be made in the absence of either direct evidence of benefit or at least, extremely powerful indirect evidence. Neither are currently available. Were there good evidence that commitment of resources of this order would result in even a 10% reduction in breast cancer mortality, the screening of younger women should surely be considered in spite of health risks, the large initial outlay required and the relatively high annual cost. To initiate screening in the absence of such evidence would require faith beyond what most individuals would consider reasonable, unless it was carried out in the context of a research study. Other output or dissemination activity: It has been well documented in official administrative correspondence that this report had a considerable influence on the position taken by the Health Department on breast cancer screening in Quebec. In November 1993, the department adopted and made public an Action Plan on Breast Cancer Screening in Quebec largely based on the recommendations made in the CETS report. The plan calls for an improvement of existing screening services and targeting activities on women 50 to 69 years old.