This article describes trends in child pornography (CP) possession cases that ended in arrest in 2000 and in 2006, using data from the National Juvenile Online Victimization Study, a two-wave longitudinal survey of a national sample of more than 2,500 U.S. law enforcement agencies. In 2006, there were an estimated 3,672 arrests for CP possession, compared with 1,713 arrests in 2000. Many characteristics of the offenders and the offense remained stable. In both 2006 and 2000, most offenders were White, non-Hispanic males and socioeconomically diverse. Few were known to have committed previous sex crimes. Most had CP that depicted preteen children and serious sexual abuse. In 2006, however, a higher proportion of offenders were aged 18 to 25 years, used peer-to-peer (p2p) networks, had images of children younger than 3 years, and had CP videos. P2p users had more extreme images (e.g., younger victims, sexual violence) and larger numbers of images than those who did not use p2p networks. Findings reflect heightened efforts in the criminal justice system to combat CP crimes. More cases originated with investigations of CP possession and involved proactive investigations aimed at detecting CP. The great majority of cases were successfully prosecuted, with more offenders sentenced to incarceration and serving longer sentences than in 2000. As in 2000, one in six cases that began with investigations of CP possession detected offenders who had molested children.