Immediately following their regular commute to work, participants completed questionnaires regarding state driver stress and anger during that commute. Then, immediately following completion of that work day, they completed a state version of the Workplace Aggression Scale. As state driver stress increased, the frequency of both expressed hostility and obstructionism increased (independently) during that work day, but only among male employees. In contrast, overt aggression during that work day was greatest among males who were higher in physical aggressiveness as a general trait characteristic. The present study highlights the interactive nature of traffic and workplace environments, in that negative experiences in the traffic environment may spill over for some individuals to influence nondriving events.