Social host laws for minors aim to reduce teenage alcohol consumption by imposing liability on adults who host parties. Parents cite safety reasons as part of their motivation for hosting parties, preferring their teens and their teens' friends to drink in a supervised and safe locale. Both sides predict an effect of social host liability for minors on alcohol-related traffic accident rates for under-aged drinkers; the effects, however, work in opposite directions. This paper finds that, among 18-20 year olds, social host liability for minors reduced the drunk-driving fatality rate by 9%. I find no effect on sober traffic fatalities. Survey data on drinking and drunk driving suggest the declines resulted mostly from reductions in drunk driving and not reductions in drinking.