This paper focuses on firm behaviour within business clusters and cluster-type environments. Using survey data to distinguish cluster members by the perceived degree of participation, the authors categorize them as leading, proactive or reactive players. They then examine the clustering behaviour of each of these categories. They find that (a) cluster development needs leaders or champions who are willing to commit time and effort to take the initiative; (b) when committed, leading players facilitate culture change so that open relationships with other cluster members can be established relatively easily; and (c) the champions of clusters are prepared to share information and knowledge in exchange for mutual benefits. Therefore, leadership and championing are matters of priority for supporters of cluster initiatives. (Contains 5 tables.)