First, a national sample of 2,574 State, county, and local law enforcement agencies was surveyed by mail to determine whether they had made arrests in Internet-related child pornography or sexual exploitation cases. A total of 2,270 agencies responded to the survey; and of these, 383 reported making 1,723 such arrests. Criteria for including a case in the study were having victims younger than 18 years old; involving arrests between July 1, 2000, and June 30, 2001; and being Internet-related. The latter criterion was met if an offender-victim relationship was initiated online; an offender who was a family member or acquaintance of a victim used the Internet to communicate with a victim to further a sexual victimization or otherwise exploit the victims; a case involved an Internet-related, proactive investigation; child pornography was received or distributed online or arrangements for receiving or distributing were made online; or child pornography was found on a computer or removable media. A total of 796 cases met all the criteria. The study found that offenders who were family members or acquaintances of victims were nearly as numerous as offenders who used the Internet to meet victims online. The family and acquaintance offenders used the Internet in their offenses as a tool to seduce or groom their victims, to store or disseminate sexual images of victims, to arrange meetings and communicate with victims, to reward victims, or to advertise or sell victims for sexual exploitation. The article advises that prevention strategies and investigative techniques should encompass such cases and their characteristics. 5 tables and 17 references