The National Juvenile Online Victimization (N-JOV) Study surveyed a national sample of 2,574 State, county, and local law enforcement agencies to determine whether they had made arrests in Internet-related child-pornography or sexual exploitation cases in the year beginning July 1, 2000. Detailed telephone interviews were then conducted with investigators who had been involved in such cases. A total of 2,270 agencies (88 percent) responded to the mail surveys. Seventeen percent of the agencies (n=383) reported 1,723 such arrests. To be eligible for the current study, cases had to have victims younger than 18; involve arrests between July 1, 2000, and June 30, 2001; and be Internet-related. Of the 1,077 eligible and sampled cases, 630 interviews were completed. The findings indicated that proactive investigations constituted 25 percent of all arrests for Internet sex crimes against minors. Such investigations were being conducted at all levels of law enforcement. The online personas assumed by investigators reflected the ages and genders of real youth victimized in sex crimes that stemmed from online encounters. These proactive investigations accessed offenders apparently less deviant in adult sexual behavior and arrest history but equally deviant with other online offenders in their possession of child pornography. Prosecutions produced high rates of guilty pleas and low rates of dismissed or dropped cases. The findings suggest that these online proactive investigative techniques can prevent the sexual victimization of minors through the Internet, obtain admissible and convincing evidence, and identify and track some offenders. 4 tables and 23 references