This essay examines theoretical, methodological, and empirical knowledge about the activation, course, and desistance from sex offending. The authors discuss theoretical issues and controversies regarding the origins and development and sex offending. Methodological issues in the measurement of sex offending and sex offending careers are reviewed, and an organizing conceptual criminal career framework is proposed to study sex offending. The current state of knowledge is presented regarding the criminal careers of juvenile sex offenders and associated developmental correlates, as well as the criminal careers of adult sex offenders and associated developmental correlates. A comparative analysis is provided of juvenile and adult sex offending careers and the respective correlates, noting developmental similarities and differences. Finally, a developmentally informed integrated model of sex offending is presented to stimulate research and policy discussion regarding the prevention of sexual violence and abuse.