Background: Violent behavior among adolescents is a significant problem worldwide, and a cross-national comparison of adolescent violent behaviors can provide information about the development and pattern of physical violence in young adolescents.Objectives: To determine and compare frequencies of adolescent violence-related behaviors in 5 countries and to examine associations between violence-related behaviors and potential explanatory characteristics.Design, Setting, and Participants: Cross-sectional, school-based nationally representative survey at ages 11.5, 13.5, and 15.5 years in 5 countries (Ireland, Israel, Portugal, Sweden, and the United States).Main Outcome Measures: Frequency of physical fighting, bullying, weapon carrying, and fighting injuries in relation to other risk behaviors and characteristics in home and school settings.Results: Fighting frequency among US youth was similar to that of all 5 countries (nonfighters: US, 60.2%; mean frequency of 5 countries, 60.2%), as were the frequencies of weapon carrying (noncarriers: US, 89.6%; mean frequency of 5 countries, 89.6%) and fighting injury (noninjured: US, 84.5%; mean frequency of 5 countries, 84.6%). Bullying frequency varied widely cross-nationally (nonbullies: from 57.0% for Israel to 85.2% for Sweden). Fighting was most highly associated with smoking, drinking, feeling irritable or bad tempered, and having been bullied.Conclusions: Adolescents in 5 countries behaved similarly in their expression of violence-related behaviors. Occasional fighting and bullying were common, whereas frequent fighting, frequent bullying, any weapon carrying, or any fighting injury were infrequent behaviors. These findings were consistent across countries, with little cross-national variation except for bullying rates. Traditional risk-taking behaviors (smoking and drinking) and being bullied were highly associated with the expression of violence-related behavior.