Breast cancer is the second deadliest cancer in U.S. women and it becomes more common as women age, so breast cancer is an important health issue for older women. Mammography involves special x-rays of the breast that can find breast cancer before it has spread. Mammography decreases breast cancer deaths in women 50 to 65 years of age, and the benefits of mammograms in this age group are thought to be worth the costs. However, whether the benefits of mammography in older women are worth the costs is unclear. While breast cancer becomes more common with age, so do other health conditions. Mammography screening might not be worth the costs in older women who are likely to die of another condition before breast cancer. Analyses that weigh the costs and benefits of mammography in women (cost-effectiveness analyses) have shown routine mammography to be cost-effective in women 65 years of age and younger, but studies have come to various conclusions about the cost-effectiveness of mammography in older women. “Cost-effective” means that the benefits are worth the costs.