Previous communication studies have focused on how media content influences human aggression. Few studies, however, have been conducted regarding the influence of situational variables on human aggression. Regarding online gaming, the present study examines how game users' aggression is influenced by two idiosyncratic situational variables: "degree of control" (playing vs. watching) and "degree of interaction" (alone vs. together). The feeling of presence is also examined as a mediator to explicate the mechanism through which these situational variables influence the game users' levels of aggression. The results demonstrate that degree of control significantly affects users' aggression. Aggression is increased when players actively participate in the game versus simply watching; situational factors that are associated with the way people engage in interactive media cause short-term shifts in players' aggression. Implications and future research directions are discussed.