The researchers found that the rates of breast cancer were similar between African-American and white women (relative risk, 1.04 [95% CI, 0.95 to 1.1]), whereas Hispanic (relative risk, 0.76), Asian (relative risk, 0.76), and Native American (relative risk, 0.53) women had significantly lower rates of breast cancer. African-American and Hispanic women were more likely than white women to be diagnosed with advanced-stage tumors, and African-American, Hispanic, and Native American women were more likely than white women to be diagnosed with high-grade tumors. Women of different races had varied frequency of mammography screening, and white women were more likely than all other groups to be “adequately screened.” In all racial groups, the rates of larger, higher-grade, and more advanced tumors increased with the time since the last mammogram. In models controlling for recency of mammography, these differences were no longer present for rates of advanced-stage, large, or lymph node–positive breast cancer between white and African-American women. However, African-American women had less favorable tumor grades than did white women, even after accounting for screening frequency.