The purpose of this paper is to investigate oleadingo firms in an industrial cluster to understand how the balance between global and local dimensions of the cluster can be managed. Two cases of industry clusters, the software and medical technology clusters in the west of Ireland, are employed to examine how certain organizations can occupy a oleado position and howif at allsuch organizations generate an agglomerative effect in a cluster. In the case of the medical technology cluster, the study shows that when large firms enact a leading role by influencing the technology trajectory of the region and stimulating the local dynamic, they can generate agglomerative effects, thereby enhancing the relevance and sustainability of clusters. Most significantly, it shows how leading organizations act as an important facilitator in connecting the global and local dimensions of clusters even in the absence of extensive local formal linkages. At the same time, the case of the software cluster reveals that the presence of large organizations alone does not inevitably stimulate such a clustering effect and emphasizes that appropriate characteristics and conditions need to be in place. Overall, while the study substantiates previous research on the significance of temporary and organized forms of proximity, it also shows the value that permanent geographical proximity can have, thereby contesting recent research that downplays the relevance of the clustering institution (e.g. Lorentzen, A. (2007) The geography of knowledge sourcingA case study of Polish manufacturing enterprises, European Planning Studies, 15, pp. 467-486; Wickham, J. Vecchi, A. (2008) Local firms and global reach: Business air travel and the Irish software cluster, European Planning Studies, 16, pp. 693-710).