On August 23, the National Cancer Institute and the American Cancer Society terminated the routine use of x-ray mammography for women under age 50 who are enrolled in a five-year joint NCI-ACS nationwide project aimed at early detection of breast cancer. The decision, announced in "interim guidelines" sent to the directors of 27 centers that have been screening a total of 270,000 asymptomatic women 35 and over, was reached after frantic deliberations that even extended to an extraordinary poll of women employees. . .