In 2008 the US Preventive Services Task Force recommended against screening men ages 75 and older for prostate cancer. Using Medicare Current Beneficiary Survey Access to Care files and linked claims, we compared trends in prostate-specific antigen (PSA) testing rates between men ages 75 and older and men ages 65-74. We estimate that the revised recommendation led to a 7.9-percentage-point decline in annual PSA testing rates over two years among men ages 75 and older. Although 42 percent of men in this age group continue to receive PSA tests, our results highlight the potential of guidelines with negative recommendations to reduce the use of low-value medical care.