The findings in this report are subject to at least six limitations. First, YRBS does not measure whether a student has driven during the 30 days before the survey, so it is not possible to assess prevalence of drinking and driving only among students who drive. According to results from the Monitoring the Future survey, 22% of 12th grade students in 2010 did not drive at all “during an average week.” Second, YRBS defines binge drinking for boys and girls as five or more drinks within a couple hours, which differs from the nationally recommended definition.** The prevalence of binge drinking among girls likely would have been higher if it were defined using a four-drink threshold, consistent with national recommendations. Third, although binge drinking and drinking and driving were strongly associated, data were not available to determine whether binge drinking occurred before driving. Fourth, the extent of underreporting or overreporting of behaviors in YRBS cannot be determined, although the survey questions demonstrate good test-retest reliability.14 Fifth, these data apply only to youths who attend school and, therefore, are not representative of all persons in this age group. Nationwide, in 2009, of persons aged 16-17 years, approximately 4% were not enrolled in a high school program and had not completed high school.15 Finally, state-level prevalence estimates of drinking and driving were not available for nine states, including four contiguous western states (Washington, Oregon, California, and Nevada).