Mackay Whitsunday Safe Communities (MWSC) was developed using a capacity building model that consciously attempted to design sustainability into the network. Our aim was to quantify the flow of resources used by MWSC to implement and sustain its injury control activities. Resource exchange among network members was quantified and analysed using social network analysis. In 2004, MWSC accessed an estimated 6.5 full-time staff equivalents and $0.9 million. However, these resources were largely accessed externally. The linking relationships that connected MWSC to its external support network, more than half of which were maintained by six broker network facilitators, were the critical social asset used to access resources and sustain network productivity. The sustainability of this network and arguably similar safety promotion networks is vulnerable to the changing priorities of external sponsoring agents and highly dependent on its leaders who facilitated access to the resources it required to remain productive.