Breast cancer mortality rates have declined in the United States and in Wisconsin. We examined racial differences in mortality trends among black and white women in Wisconsin and the United States from 1979 to 1996. During this time period, mortality rates increased 10% among black women and decreased 7% among white women in Wisconsin. These trends were similar nationally, with an 18% increase among black women and a 3% decrease among white women. The black:white gap in mortality increased among women of all ages--especially among women under age 55. The increasing racial disparity in breast cancer mortality may result from differences in trends in incidence and survival among black women. More research is needed to understand the underlying causes of the disparity in breast cancer mortality between black and white women.