This study investigated the prevalence of Internet addiction among South Korean adolescents and explored family factors associated with such addiction. The study participants were middle and high school students residing in Seoul. One-tenth (10.7%) of the 903 adolescents surveyed scored at least 70 on the Internet Addiction Scale. These youths were considered at high risk for Internet addiction and in need of further assessment and intervention. Results show that parenting attitudes, family communication, family cohesion, and family violence exposure (e.g., conjugal violence and parent-to-child violence) were associated with Internet addiction. These findings indicate that families play an important role in preventing Internet addiction and must be considered when programs are developed to minimize excessive Internet usage by high-risk adolescents. (Contains 3 tables.)