Conduct disorder (CD) is public health challenge in Africa were rates are high. CD refers to a pattern of behavior including aggression, destruction of property, deceitfulness, theft and violation of rules. Adolescent CD is linked to high risk behaviours such as smoking, substance abuse, early sexual debut and to violent behaviours like participating in gangs, using weapons to harm, sexual coercion, and risk of arrest. In adulthood CD is associated with antisocial and violent behaviours and poor longer term health outcomes, but the pathways to these outcomes are complex, and poorly understood. Previously, we established a link between CD, Executive Functions (EFs) and violent behaviours in primary school-aged rural children. EFs are necessary for planning, problem solving and decision-making and EF impairments are linked to violence, substance misuse and risk-taking. Importantly, EFs are modifiable. This project investigates this association in early adolescence (11-13 years), a period of rapid development and escalating risk, collecting repeated measures from 1486 adolescents in urban Soweto, South Africa. We test the hypothesis that cognition, specifically deficits in EFs, underlies violent and risky behaviour amongst adolescents with CDs investigating which components of EF relate to which outcomes, and advancing a mechanistic understanding which could optimise interventions. Conduct disorders (CD) involve persistent patterns of behavior including aggression, destruction of property, deceitfulness, theft and violation of rules. Adolescent CD is linked to risk behaviours (smoking, substance use) and violent behaviours (use of weapons, sexual coercion). In adulthood they link to antisocial behaviour and are costly to society. Globally 5% of adolescents have CD; in African estimates are double that. Although difficult and expensive to treat, CD can be treated; however there is little evidence on interventions that work for adolescents. Previously, we found a link between CD and Executive Functions (EF) in younger children. EFs are mental processes important for planning, decision-making and managing frustration. EF may play an important role in violent and risky behaviour amongst CD adolescents. This project explores this link in 1486 urban adolescents in South Africa, investigating whether behavioural interventions can be enhanced by improving EF, with enormous potential for optimising behavioural interventions.