This article assesses the promise of motor vehicle passengers as interveners to prevent drinking and driving. It describes data from the U.S. Fatal Accident Reporting System (FARS), which indicate that most alcohol-involved fatally injured drivers (70% of males, 66% of females) were not accompanied by "adult" passengers (16 or older), and alcohol involvement among those passengers present appears to be high (80%). Nonetheless, in approximately 5% to 10% of cases it appears that sober or relatively "unimpaired" passengers could have served as interveners in alcohol-involved driving incidents. Passenger interveners may hold the most promise among teenagers, where passengers in general and unimpaired passengers in particular appear to be most prevalent.