A new study presented at the 2009 American Association for Cancer Research International Conference on Frontiers in Cancer Prevention Research has found that only some of the estimated 7% decline in breast cancer incidence since 2002 can be attributed to a decline in combined hormone replacement therapy (HRT) use. The decline in breast cancer incidence since 2002 has been widely attributed to discontinuation of HRT use following the Women’s Health Initiative randomized trial. However, very little analysis has been conducted to quantify the relationship. Using an estimated 46% decline in HRT use and a relative risk for current use of 1.5, the authors estimate that 42% of the decline in breast cancer incidence is attributable to cessation of hormone use. The authors conclude that cessation of postmenopausal hormone use following the 2002 announcement of an association between HRT use and breast cancer is unlikely to account for more than half of the observed decline in breast cancer incidence among women aged 40-79 years old. The potential contributions of other factors should be examined in future studies, especially the role of the recent plateau in use of breast cancer screening.