It appears that Challenge Grant funding was associated with virtually no overall decline in juvenile arrests. This finding suggests that the funding could have been better directed elsewhere, particularly when estimates of arrests prevented were calculated on the basis of the program’s overall effect across funded counties. However, when county-specific estimates were calculated, it appeared that some counties witnessed fairly dramatic reductions in arrest activity that was associated with Challenge Grant funding. Collaboration and partnerships throughout criminal justice constitute a fairly recent development. Both public and private agencies are increasingly joining forces in an effort to address a wide array of social problems. Most of the research concerning collaboration in criminal justice involves the bringing together of traditional criminal justice actors, such as police, court officials, and corrections personnel. Despite these developments, surprisingly little research exists concerning the effect of multiagency collaboration on juvenile crime and delinquency. This analysis of California’s Challenge Grant Program which has funded 14 collaborative efforts is hoped to contribute to the literature concerning collaboration and multi-agency partnerships in criminal justice. Panel data were analyzed to determine whether funding for collaborative juvenile crime prevention programs reduced arrests in California counties. Appendix, tables and references