Women aged 75 and older are the fastest growing segment of the US population. Yet, none of the mammography screening trials included women over age 75, and it is not clear whether mammography results in a mortality benefit for these women. While the benefits of mammography are uncertain, particularly for older women with short life expectancies, there are important harms to screening including: pain and anxiety related to the test, complications from additional tests after a false positive mammogram (e.g., breast biopsy), and overdiagnosis (diagnosis of tumors that are no threat in one's lifetime). Overdiagnosis is particularly concerning since risks of breast cancer treatment increase with age. Guidelines state that there is insufficient evidence to recommend mammography for women >75 years and recommend that older women be informed of the uncertainty of benefit and potential for harm. They further encourage clinicians to consider patient health and life expectancy before offering screening. Meanwhile, Medicare covers annual mammograms for all women >65 years and many older women are screened regardless of their life expectancy. Thus, few older women are informed of harms of mammography and most overestimate the benefits. To improve older women's decision- making around mammography screening, we developed and pilot tested a mammography screening decision aid (DA) for women >75 years. The DA, a self-administered, easy-to-read, pamphlet, includes information on outcomes of screening, breast cancer risk, health and life expectancy, competing mortality risks, and a values clarification exercise. Our pilot pretest/posttest trial of the DA included 49 women >75 years (range 75-86 years) from a large Boston academic primary care practice and found that the DA improved knowledge, decreased decisional conflict, reduced intentions to be screened, and led to more balanced mammography discussions with their physician. We, a team of internists, geriatricians, and a psychologist, now propose a large randomized controlled trial (RCT) of the DA to definitively evaluate its efficacy. We aim to show that the DA improves older women's knowledge of the pros and cons of mammography, decreases decisional conflict, and reduces screening intentions, particularly for women with <7 year life expectancy. We also aim to show that the DA leads to increased chart documentation of balanced mammography discussions and reduces screening, particularly for women with <7 year life expectancy. We will recruit from an academic primary care and geriatrics practice in Boston, 3 Boston area community practices, and an academic and community practice in North Carolina. We plan to randomize 520 women ages 75-89 years to the DA (intervention arm) or an educational pamphlet on home safety for older adults (control arm). It is essential that we test our DA in a large RCT to know if it is truly effective. Such compelling RCT data are needed to support second-order translation (research to clinical practice) of the DA nationally within primary care. Our DA has the potential to improve older women's mammography screening decisions, thereby improving their care and quality of life.