Two selective estrogen receptor modulators, tamoxifen and raloxifene, have been shown in randomized clinical trials to reduce the risk of developing primary invasive breast cancer in high-risk women. In 1998, the U.S. Food and Drug Administration (FDA) used these studies as a basis for approving tamoxifen for primary breast chemoprevention in both premenopausal and postmenopausal women at high risk. In 2007, the FDA approved raloxifene for primary breast cancer chemoprevention for postmenopausal women. Data from the year 2010 National Health Interview Survey were analyzed to estimate the prevalence of tamoxifen and raloxifene use for chemoprevention of primary breast cancers among U.S. women. Prevalence of use of chemopreventive agents for primary tumors was 20,598 (95 % CI, 518-114,864) for U.S. women aged 35-79 for tamoxifen. Prevalence was 96,890 (95 % CI, 41,277-192,391) for U.S. women aged 50-79 for raloxifene. Use of tamoxifen and raloxifene for prevention of primary breast cancers continues to be low. In 2010, women reporting medication use for breast cancer chemoprevention were primarily using the more recently FDA approved drug raloxifene. Multiple possible explanations for the low use exist, including lack of awareness and/or concern about side effects among primary care physicians and patients.