Evidence from clinical trials suggests that increasing the use of mammography will lead to declines in breast cancer mortality. We analyzed trends in age-adjusted and age-specific breast cancer mortality in Wisconsin from 1979 to 1996. From 1979 to 1990, age-adjusted mortality rates among women of all ages increased about 0.7% per year, a result primarily of increasing rates among women 65 years of age and older. Since 1990, rates have decreased 3.4% per year. These data suggest that mammography is effective in reducing breast cancer mortality in the state. Wisconsin should reach its Year 2000 objective of reducing breast cancer mortality.