Gang violence creates serious safety and security concerns in the community and prisons. Treated gang and nongang members recidivated significantly less in a 24-month follow-up than their untreated matched controls. Treatment consisted of high intensity cognitive-behavioral programs that follow the risk, need, and responsivity principles (Andrews & Bonta, 2003). The treated gang members who recidivated violently after treatment received significantly shorter sentences (i.e. they committed less serious offences) than their untreated matched controls. Untreated gang members had significantly higher rates of major (but not minor) institutional offences than the other three groups. Correctional treatment that follows the risk, need and responsivity principles appears able to reduce recidivism and major institutional misconduct. Effective correctional treatment should be considered as one of the approaches in the management and rehabilitation of incarcerated gang members.