How do organisations collaborate in the daily practice of law enforcement? And what role plays autonomy of government agencies within this cooperation? In this article the authors answer these questions on the base of two case studies: two large scale projects in which a partnership approach was used to combat human trafficking in the Netherlands. Collaboration between city administration, investigation services and tax authorities seems to be very hard to put into practice. This is understandable from the theory that government agencies, while performing their tasks, are focused on achieving autonomy.