Black women die of breast cancer at a much higher rate than white women. Recent studies have suggested that this racial disparity might be even greater in Chicago than the country as a whole. When data describing this racial disparity are presented they are sometimes attributed in part to racial differences in tumor biology. Vital records data were employed to calculate age-adjusted breast cancer mortality rates for women in Chicago, New York City and the United States from 1980-2005. Race-specific rate ratios were used to measure the disparity in breast cancer mortality. Breast cancer mortality rates by race are the main outcome. In all three geographies the rate ratios were approximately equal in 1980 and stayed that way until the early 1990s, when the white rates started to decline while the black rates remained rather constant. By 2005 the black:white rate ratio was 1.36 in NYC, 1.38 in the US, and 1.98 in Chicago. In any number of ways these data are inconsistent with the notion that the disparity in black:white breast cancer mortality rates is a function of differential biology. Three societal hypotheses are posited that may explain this disparity. All three are actionable, beginning today.