Preferential sex offenders tend to be predatory serial offenders and can usually be identified by long-term and persistent behavior patterns, specific sexual interests, and fantasy-driven behavior. They often suffer from paraphilias, psychosexual disorders that involve recurrent, intense, and sexually arousing fantasies and from sexual urges and behaviors that usually involve nonhuman objects, the humiliation of oneself or one's partner, and children or other nonconsenting persons. In child sex ring and pornography cases, offenders typically control their victims by seducing them with attention, affection, kindness, and gifts until they have lowered the victim's inhibitions and gained his or her cooperation and consent. Because of their bond with the offender, victims frequently resent law enforcement intervention and may even warn the offender. The investigation of child sexual exploitation cases involving multiple victims molested by preferential offenders is usually complex and difficult. Guidelines are presented for interviewing victims and offenders, investigating offenders, recovering child exploitation evidence, obtaining expert search warrants, and conducting an effective prosecution. Special procedures to follow when investigating child sexual exploitation cases involving computers are noted, and types of offenders who engage in child pornography using computers are identified. An investigator's checklist for interviewing victims of preferential sex offenders is included. 6 references