Little is known about the relationship between firearm carrying and hostile behavior on the roadway. To explore a possible association between firearm carrying by drivers and hostile driving behavior we conducted a random-digit-dial survey of 790 licensed drivers in Arizona. In addition to demographic questions, we asked whether respondents had carried a gun while driving in the 12 months prior to the survey. Respondents were also asked if they, in anger, had personally made obscene gestures, cursed or shouted at other drivers, impeded another drivers progress with their vehicle, aggressively 'followed another driver too closely', or brandished a gun at another driver. We used multivariable logistic regression to explore correlates of hostile driving behavior while taking into account several demographic and behavioral characteristics. Overall 11% of drivers always (4%) or sometimes (7%) carried a gun with them in their vehicle; 34% report having made obscene gestures/cursed/shouted angrily; 28% report aggressively following or blocking other drivers with their vehicle. In both crude and multivariate adjusted analyses, self-report of engaging in hostile behavior while driving was significantly more common among men, young adults, and individuals who carried a firearm in their car. Our findings suggest that, at least among Arizona motorists, having a gun in the car is a strong marker for aggressive and illegal behavior behind the wheel.