Based on a wide-ranging literature review, we argue that the information and communications technology infrastructure has not received adequate attention for its role in the development and maintenance of industrial clusters. This paper develops expectations for how firms in an industrial cluster make use of a public, broadband ICT infrastructure, particularly in support of e-commerce applications. We further address the question of whether ICT use, by enabling stronger ties to non-cluster partners, can weaken clusters. A case study of a successful biotechnology cluster in Denmark and Sweden – the Medicon Valley – is used to explore ICT use in a knowledge-intensive cluster context. We conclude that ICT use appears to strengthen rather than weaken the Medicon Valley cluster, and that firms located within a cluster appear to gain some unique advantages from their ICT usage that are not necessarily available to firms outside the cluster.