4 Background: A woman’s understanding of her breast cancer risk is an important precursor for care. A valid estimate allows for greater opportunity to consider early detection modalities and chemopreventive medications. The USPSTF recently encouraged women who have an increased risk of developing a first breast cancer and a low risk of side effects to take tamoxifen or raloxifen. The objective of this study is to compare patients' perceived breast cancer risk with their calculated risk and then parse those findings by ethnicity. Methods: Anonymous, IRB approved, pre-piloted questionnaires were filled out by women at 21 mammography centers on Long Island. The survey included questions about patient demographics, patient’s estimates of their own breast cancer risk and personal risk factors. Results: 9,873 respondents qualified for inclusion in our analysis. Women were asked to quantify their breast cancer risk by age 90. Overall, 707 (9.4%) were in line with their risks, 3,359 (44.7%) underestimated risk and 3,454 (45.9%) overestimated their risk. When parsed by ethnicity, of the 781 African Americans, 8.7% were in line, 57.6% underestimated risk, and 33.7% overestimated risk. Of the 245 Asians, 10.2% were in line, 58.8% underestimated risk, and 31% overestimated risk. Of the 427 Hispanics, 8.9% were in line, 50.4% underestimated risk, and 40.8% overestimated risk. Of the 6850 Caucasians, only 10.2% were in line, 38.6% underestimated risk, and 51.3% overestimated risk. Conclusions: Most women lack accurate knowledge of their own breast cancer risk – 90.6% overall. When parsed by ethnicity, while there was a statistical difference between groups, the difference was not important because overall understanding was very low. Caucasian women tended to overestimate their risk compared with other ethnic groups, possibly resulting in unnecessary anxiety. African American and Hispanics tended to underestimate risk compared with Caucasians, possibly resulting in underutilization of available resources. Patients must have a better understanding of their personal risk. Study findings should help refocus educational efforts because increased knowledge of breast cancer risk will enable providers to tailor an individual’s medical treatment plan.