BACKGROUND:Limited scientific evidence is available regarding D/deaf women's breast cancer knowledge and early detection practices, as well as about how to increase D/deaf women's breast cancer control practices. OBJECTIVE/HYPOTHESIS:To assess baseline breast cancer knowledge and practices among a sample of D/deaf women recruited into a randomized controlled trial of a breast cancer education program developed for this population. METHODS:A written and signed (American Sign Language) survey was administered to a racially/ethnically diverse sample of 209 D/deaf women, 40+ years old, with lower levels of education, recruited in California between October 2008 and May 2009. RESULTS:There were misconceptions about breast cancer risk factors, screening, and treatment; only 64.2% of respondents correctly identified the purpose of mammography. Mammography in the prior 2 years was reported by 57.3% of the sample, by 69.8% of White women, and by 43.5% of women from other racial/ethnic groups. Rates also varied by education, having seen a physician in the prior year, and type of insurance. CONCLUSIONS:This study underscores significant gaps in breast cancer screening knowledge and practices, communication issues in health care settings, and unmet needs for tailored health information and materials in this population. Challenges faced in conducting the research needed to develop and test such programs are noted.