The ISVYOS has been in operation since 1998 and is the most extensive survey of incarcerated youth in Canada. The ISVYOS is separated into two cohorts. Cohort I was interviewed between 1998-2003 during Canada’s Young Offender Act legislation. Cohort II was interviewed between 2005-2011 during Canada’s Youth Criminal Justice Act. The ISVYOS includes information collected from the youth during interviews and from official criminal justice files. The purpose of the study is to identify risk factors in adolescence that predict which youth are likely to continue offending in adulthood. The main concepts under examination include: the needs profiles of incarcerated youth, risk factors for gang involvement and the network structure of gangs, differences in risk factors for males and females, the role of foster care, explanations for early mortality, and explanations for serious and violent crimes such as homicide, sexual assault, and gun carrying.