OBJECTIVE. The goal was to examine the association between violence in the media and the expression of seriously violent behavior among older children and teenagers in a national sample. METHODS. The Growing up with Media survey was a national, online survey of 1588 youths that was conducted in August and September 2006. Participants were 10- to 15-year-old youths who had used the Internet at least once in the past 6 months. The main outcome measure was self-reported seriously violent behavior, including (1) shooting or stabbing someone, (2) aggravated assault, (3) robbery, and (4) sexual assault. RESULTS. Five percent of youths reported engaging in seriously violent behavior in the past 12 months. Thirty-eight percent reported exposure to violence online. Exposures to violence in the media, both online and off-line, were associated with significantly elevated odds for concurrently reporting seriously violent behavior. Compared with otherwise similar youths, those who indicated that many, most, or all of the Web sites they visited depicted real people engaged in violent behavior were significantly more likely to report seriously violent behavior. After adjustment for underlying differences in youth characteristics, respondents' alcohol use, propensity to respond to stimuli with anger, delinquent peers, parental monitoring, and exposures to violence in the community also were associated with significantly increased odds of concurrently reporting seriously violent behavior. CONCLUSIONS. Exposure to violence in the media is associated with concurrent reports of seriously violent behavior across media (eg, games and music). Newer forms of violent media seem to be especially concerning. Pediatrics 2008; 122: 929-937