The file describes the data of the SNARE project (Social Networks and Risk Behavior in Early Adolescence). This was a longitudinal research project on the social development of early adolescents with a specific focus on adolescents’ peer relationships and their involvement in risky behavior, including both self-reported data and peer-nomination data. All first-year and second-year students in two secondary schools in the Netherlands were approached to take part in the project (Cohort 1) at the beginning of the academic year 2011–2012. A second cohort of students entering their first year in these secondary schools was asked to take part in the project the following academic year 2012–2013 (Cohort 2). Data were collected three times in one academic year (in the fall, winter, and spring), starting in 2011–2012 (Cohort 1) and 2012–2013 (Cohort 2), respectively. In total, 12 waves of data have been collected. Before data collection started, students received an information letter describing the goal of the study and offering the possibility to refrain from participation. Parents who did not wish their children to participate in the study were asked to indicate this and students were made aware that they could cease their participation at any time. The survey was completed in the classroom by computer, supervised by a researcher, using Bright Answer socio software (SNARE software 2011). The privacy and anonymity of the students were warranted, and the study was approved by the Internal Review Board (IRB) of Utrecht University (see also Franken et al. 2016; the project name is “Social Network Processes and Social Development of Children and Adolescents”).