In 2009, the United States Preventive Services Task Force (USPSTF) recommended against routine mammography screening for women aged 40–49 years. This revised recommendation was widely criticized and has sparked off intense debate. The objectives of this study are to examine the impact of the revised recommendation on the proportion of women receiving mammograms and how the effect varied by age. Methods: We identified women who had continuous health insurance coverage and who did not have breast cancer between 2008 and 2011 in the Truven Health MarketScan Commercial Claims Databases using mammogram procedure codes. Using women aged 50–59 years as a control group, we used a differences-in-differences approach to estimate the impact of the revised recommendation on the proportion of women ages 40–49 years who received at least one mammogram. We also compared the age-specific changes in the proportion of women ages 35–59 years who were screened before and after the release of the revised recommendation. Results: The proportion of women screened among the 40–49 and 50–59 age groups were 58.5 and 62.5%, respectively, between 2008 and 2009, and 56.9 and 62.0%, respectively, between 2010 and 2011. After 2009, the proportion of women screened declined by 1.2 percentage point among women aged 40–49 years (P  <  0.01). The proportion of women screened decreased for all ages, and decreases were larger among women closer to the 40-year threshold. Conclusions: The 2009 USPSTF breast cancer recommendation was followed by a small reduction in the proportion of insured women aged 40–49 years who were screened. Reductions were larger among women at the younger end of the age range, who presumably had less prior experience with mammography than women nearing 50.