This chapter focuses on child molesters who abuse children from outside of their families (extra-familial). The vast majority of research on child molesters focuses on adult male offenders, but information about female sexual offenders is presented when available. Extra-familial child molesters share a variety of common characteristics, including chaotic family backgrounds, physical or sexual parental abuse, early childhood sexualization, and prior victimization. The effects of child sexual abuse and the likelihood of sex offender recidivism are briefly reviewed before the author describes the major theoretical perspectives that have been used to explain extra-familial child molestation. In general, theories that explain child molestation combine criminological and psychological aspects. Behavioral theory regards sexual deviation as a learned behavior in which child molesters re-enact their own victimization. Cognitive-behavioral theory focuses on child molester’s thoughts and feelings, claiming that child molesters become preoccupied with deviant fantasies. Cognitive-behavioral therapies are widely considered the most appropriate treatment approaches for child molesters. Cognitive-behavioral therapy (CBT) focuses on preventing future sex offending by teaching the offender to recognize the links between thoughts, emotions, and beliefs about offending. The author reviews the goals and challenges associated with sex offender treatment. Main goals include the reduction of deviant arousal and cognitive distortions and the enhancement of self control. Evaluation research on sex offender treatment approaches is summarized, which generally suggests that a combination of group treatment and individual therapy works better than either in isolation and that residential community programs are more effective than prison-based programs. The author offers a brief section on “other populations” of child molesters, focusing on adolescent and female offenders, both of which are rare. Note, references