The Campbell Collaboration Crime and Justice Group was inaugurated in 2000 to prepare, update, and disseminate systematic reviews on what works to reduce crime or improve justice. After providing a brief description of a systematic review and the origins of the Campbell Collaboration, this paper provides an overview of the first 36 months of the Crime and Justice Group. Some of the reviews within its portfolio focus on treatment of offenders, including cognitive-behavioral programs, community-based programs for juveniles, prison-based drug treatment, and sex offender therapy. Through its electronic publication known as C2-RIPE, the Campbell Collaboration aims to provide an up-to-date, easily accessible, scientifically reputable, and evidence-based resource that treatment professionals and others can consult. (Contains 4 figures.)