This paper explores the extent and effectiveness of proactive investigations in which investigators pose as minors on the Internet to catch potential sex offenders. It utilizes a subsample of cases from the National Juvenile Online Victimization Survey, which concerned persons arrested for Internet sex crimes against minors in the year beginning July 1, 2000. Results suggest proactive investigations represented a significant proportion (25%) 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 paralleled the ages and genders of real youth victimized in sex crimes that started as online encounters. These proactive investigations accessed an offender group that appeared somewhat less deviant in terms of adult sexual behavior and arrest history but equally deviant as other online offenders in terms of possession of child pornography. Prosecution of these cases produced high rates of guilty pleas and low rates of dismissed or dropped cases. The entrapment, fantasy or role-playing, and factual impossibility defenses were used but not successfully. Findings suggest that the Internet sometimes allows law enforcement to interdict before a youth is victimized, gather solid evidence of offenses, and find and track some offenders.