 This randomized, controlled trial is designed to test whether short-term 1-2 months HRT cessation will sufficiently lower breast density to decrease the proportion of women who receive a recommendation for additional evaluation following a screening mammogram, and to examine whether there is a trend by duration of cessation. The study is being conducted at Group Health Cooperative, a managed health care organization in western Washington State with an organized breast cancer screening program. We are recruiting 1,500 women and will randomize women to one of three HRT arms: 1 cessation two months before the screening mammogram; 2 cessation one month before; and 3 continued HRT use. We are using a computer-assisted method to measure mammographic breast density continuously. Mammography recall rates are being determined from an expert radiologist review of the mammograms, blinded to HRT status. 