The use of all-terrain vehicles (ATVs) has increased in the United States and elsewhere over the last three decades, along with an increased frequency of incidents resulting in serious injuries, among which have been head injuries. ATVs are designed for motorized off-highway work and recreation, can weigh up to 600 lbs (272 kg), and may reach speeds as high as 75 mph (120 km/h). ATV crashes, including collisions and overturns, were responsible for 8104 fatalities from 1982 to 2006. One third of those killed were youth under 16 years of age. Helmets may reduce risk of death by 42% and nonfatal injury by 64%. In this study, a decision analysis was applied to determine the potential reduction in the rate of fatal and nonfatal head injuries associated with crashes, based upon the universal wearing of head protection while riding on ATVs. In addition, based upon this reduction in injury rate, a cost-effectiveness analysis was conducted to determine the savings per injury averted among ATV riders with head protection. The authors found that 238 head injuries, including 2 fatalities per 100,000 ATV drivers with an average of 145 hours of annual operation, could be averted by the universal wearing of head protection while riding on ATVs. Taking into account the social direct and indirect costs of fatal and nonfatal head injuries at a 5% discount rate, US$364,306 could be saved per injury averted over a 50-year period if there were universal wearing of head protection by ATV drivers. If the exposure is adjusted to 2000 hours per year for an equivalent work year, 3276 head injuries could be averted including 23 fatalities per 100,000 at a social cost savings of US$509,172.