Although age is the most important risk factor over long age intervals, it is not as important as other risk factors at the ages of 40 to 50 years. In 1998, Gail and Rimer (2) suggested that a woman in her 40s should consider mammography screening if her absolute risk was as great as that of a 50-year-old woman without other risk factors. Benefits are believed to outweigh risks in a 50-year-old woman, and Gail and Rimer say the same should be true for a younger woman with similar risk. The ratio of incidence rates of a 50-year-old white woman with no risk factors versus a 40-year-old white woman with no risk factors is 2.46 (2). If the 40-year-old woman has risk factors that increase her risk at least 2.46 times above baseline, she has at least the absolute risk of the 50-year-old woman. Many risk factors, such as having 2 affected first-degree relatives, atypical hyperplasia, and at least 75% dense tissue on mammography, have relative risks that exceed 2.46, as do many combinations of weaker risk factors (2–3). For a 48-year-old woman, risk factors need to increase baseline risk by only 6% to put her at the risk of a 50-year-old woman with no risk factors (2).