American Indians, especially those residing in the Northern Plains, experience considerable preventable morbidity and mortality from alcohol-related motor vehicle events. Research focusing on unintentional injuries associated with drinking drivers has disregarded the epidemiology of their passengers, who are equally at risk. The purpose of this investigation was to define the prevalence of motor vehicle passengers riding with drivers who have been drinking on a Northern Plains Reservation. We surveyed a sample of 151 Northern Plains Indians about their experiences riding with drinking drivers. Associated behavioral and demographic risk factors were also examined to identify possible predictor variables. The majority (54%) of respondents reported riding with a driver who had been drinking at least once during the previous three months. Most often, passengers ride with a friend who has been drinking, on a weekend night. Injury risk may be compounded because few respondents reported regular seat-belt use. The results off our study suggest the need for immediate comprehensive prevention efforts focusing on motor vehicle passengers.