In this article, we study how the configuration of a publicly promoted clusters policy-the Global Clusters policy initiated by the Walloon Government in Belgium-influenced the behaviors of R&D practitioners. At first, we explored the background of the Global Cluster policy in an effort to make the program configuration visible. This first step was conducted through the gathering and analysis of data from official documents as well as publications, conference speeches and workshops produced by policy makers, evaluators and their academic collaborators. Then, we observed the transmission of the six resulting features from the policy level to the project level: we studied their appropriation by R&D practitioners in "Mirage", an R&D project associated to the mechanical engineering Global Cluster. As a result, we show that the particularities of Walloon Global Clusters make them a powerful instrument to enhance collateral assets while facing potential lock-in. We finally consider the way these Global Clusters should evolve to favor the exploitation of the emerged outcomes while exploring future opportunities. A good balance between exploitation and exploration as well as adequate networking and clustering instruments to support both objectives appear necessary to ensure sustainability and growth of the involved actors. © 2010 Springer Science+Business Media, LLC.