This study advances research on media literacy by comparing the effectiveness of two versions of a media literacy intervention over time. Participants (156 children in 4th or 5th grade) were randomly assigned to one of two treatment groups or a control group. Both treatment groups were exposed to an instructional intervention designed to reduce the negative effects of media violence. One of the groups was given an additional cognitive activity immediately following the instructional intervention. Participants in all 3 groups had their aggressive tendencies measured at 4 points in time. Results indicate that when the children participated in a cognitive activity after receiving the media literacy intervention, they experienced an immediate reduction in willingness to use aggression after exposure to violent media. However, the same media literacy intervention without the cognitive activity led to an increase in willingness to use aggression. Our longitudinal results indicate that children receiving an intervention without a cognitive activity might also remain more willing to use aggression over time. (Contains 3 figures.)