**2. Methods**

The Growing up with Media study is a longitudinal survey examining the associations between exposure to violent media - particularly new media (e.g., the Internet) - and violent behavior. Wave 1 data were collected August-September, 2006 with 1,588 youth-caregiver pairs; data were collected again November, 2007 - January 10, 2008 [Wave 2, (n=1,206)] and August - November, 2008 [Wave 3, (n=1,159)]. The survey protocol was reviewed and approved by the Centers for Disease Control and Prevention Institutional Review Board (IRB).

The sample was obtained from the Harris Poll Online (HPOL) opt-in panel (Harris Interactive, 2006), which is comparable to random telephone samples of adult populations once appropriate sample weights are applied (Berrens, Bohara, Jenkins-Smith, Silva, & Weimer, 2003; Berrens, Bohara, Jenkins-Smith, Silva, & Weimer, 2004; Schonlau et al., 2004; Taylor, Bremer, Overmeyer, Siegel, & Terhanian, 2001). Recruitment was balanced on youth age and sex. Participants were recruited through an email contact with randomly identified adult HPOL members who had previously indicated a child lived in the household. Adult respondents (one per household) were required to be equally or more knowledgeable than other adults in the home about the youth's media use, and to provide consent for their participation and permission for their child's participation. Youth participants were required to be 10-15 years old, read English, live in the household at least 50% of the time, have used the Internet in the last 6 months, and provide assent to participate in research.

On average, adult surveys lasted 5-minutes and youth surveys 21 minutes. Youth received a \$20 gift certificate and caregivers a \$15 check for their participation at Waves 1 and 2; and \$25 and \$20, respectively at Wave 3. The surveys were administered by Harris Interactive.
