This review concludes that exposure to media violence increases the risk of both children and adults behaving aggressively in the short-run, and of children behaving aggressively in the long run. As with other public health threats, not every child who is exposed to this threat will acquire the affliction of violent behavior and many will acquire the affliction though not exposed to the threat. Children’s exposure to media violence increases the risk significantly that the viewer or game player will behave more violently both in the short term and long run. Randomized experiments demonstrated conclusively that exposure to media violence immediately increased the likelihood of aggressive behavior for both children and adults in the short run. The evidence from longitudinal field studies is also compelling that children’s exposure to violent electronic media, including violent games, leads to long-term increases in their risk for behaving aggressively and violently. These long-term effects are a consequence of the powerful observational learning and desensitization processes that neuroscientists and psychologists now understand to occur automatically in children. Children automatically acquire scripts for the behaviors they observe around them in real life or in the media, along with emotional reactions and social cognitions that support these behaviors. Social comparison processes also lead children to seek out others who behave in similar aggressive manners in the media or in real life, leading to an increased risk for violent behavior; the size of the effect is large enough that it should be considered a public health threat. Second the effect size of media violence is the same or larger than the effect size of many other recognized threats to public health; the only effect slightly larger than the effect of media violence on aggression is that of cigarette smoking on lung cancer. Figure, references