In the paper, we present how transnational corporations (TNCs) internationalize their R&D and how they allocate foreign R&D units in high-tech clusters, where competitors of these TNCs, research and academic institutions, and suppliers of these TNCs are also located. We confront two paradigms of R&D internationalization (traditional and new one) and we determine what are the main motives that drive R&D internationalization of TNCs. Based on a modern innovation theory, we derive a cluster approach as a specific method of analyzing modern R&D internationalization.  We then present an analysis of two high-tech clusters (Cambridge, Bangalore) and we show that some TNCs allocate their foreign R&D units into those clusters, in order to make use of available external knowledge from academic institutions through intensive R&D collaborations.