Less frequent mammograms for wonem at low risk for breast cancer can be a cost effective way of saving lives. Women with no family history of breast cancer, no previous biopsy and breasts that are not dense need far fewer mammograms than women with these risk factors. For women under the age of 50 without these three risk factors, mammograms are not worthwhile. To save one life among women under the age of 50, 8000 women would have to be screened and 17% would experience a false positive cancer scare that would lead to more radiation and a biopsy. Women with dense breasts under age 50 would benefit from a mammogram every three to four years. For older women without these three risk factors, it is cost effective to do mammograms every 3-4 years. For those with denser breasts, every two years is recommended.