Universal helmet laws (UHLs) are widely believed to be effective in reducing motorcycle fatalities. In this chapter, we further investigate the effectiveness of such policies by focusing on their long-term impact as well as their effect on motorcycle use. Using state-level longitudinal data from 1975 to 2005, we estimate how the adoption and repeal of UHLs influence motorcycle safety. Our results confirm earlier findings that adoption of UHLs prevents fatalities, whereas repeals lead to higher fatality rates. We provide evidence that UHLs operate as intended, decreasing fatalities mainly by improving safety rather than by reducing motorcycle riding. Finally, using dynamic specifications, we show that the long-term effects of both adoption and repeal persist in the years beyond the policy change.