18–21 Although in 2012 31 US states had a helmet requirement for ATV riders, these regulations include various qualifiers such as when and by whom helmets must be worn, and exceptions for age requirements if a child is supervised by an adult, riding on private property, or has a safety certificate. 22 Effectiveness studies of such state imposed regulations in reducing injuries and deaths among young riders have produced equivocal results. 13 ,20 ,23–25 Enforcement of these regulations is limited in part because many states’ laws pertain only to the use of ATVs on public lands, and according to a 2008 ATV owners’ survey obtained by the US Government Accountability Office, nearly 80% of ATV riding among riders of all ages occurs on private property. 26 Further evaluation of the effectiveness of ATV helmet regulations and enforcement strategies is needed. 27This study has limitations. First, the YouthStyles survey was not administered to a nationally representative random sample of US youth.