This is the final Policy Brief in a series of three about youth gangs and the prevention of youth crime. In Policy Brief 1 we noted that crime becomes more likely when risk factors such as early childhood experiences, broken family life, school failure and unemployment accumulate. In the second Policy Brief examples of prevention programmes in separate sectors such as the school, the community, and the family were presented. In this Policy Brief we discuss opportunities and challenges of multi-agency partnerships that integrate different actors of social control: the government, local authorities, and the community. The three Policy Briefs are published in a condensed form in the Final Report to the project "Youth Gangs".