This article examines the effectiveness of helmets in reducing all-terrain vehicle (ATV) related deaths and head injuries, conditional on the occurrence of injury producing accidents. A logit regression model is used to analyze cross-section data on ATV-related fatal and nonfatal injuries, and to determine the factors that are associated with deaths and head injuries. The results suggest that, given an accident resulting in injury or death, helmet use reduces the risk of death by about 42%, and could reduce the likelihood that a given nonfatal injury involves the head by about 64%. Other factors that are associated with the risk of fatality for injury accidents include the use of alcohol or drugs, driving on paved roads, the driver's age and sex, and the vehicle's engine size. A benefit-cost analysis of helmet use is conducted and policy implications are discussed.