Biomedical innovation typically involves intense collaboration across diverse disciplines, occupations and organizations. Given this, a nation's integrative capabilities (the ability to move between basic science and clinical development) and relational capabilities (the ability to collaborate with diverse organizations) have been identified as crucial for encouraging innovation. However, the impact of such capabilities on innovation has been considered, to date, mainly in macro, structural terms -explaining US national competitive advantage, for example. This paper draws, instead, from a qualitative analysis of biomedical innovation in the UK and US to identify mechanisms influencing innovation at the project level through which macro level capabilities may be having effects. From this we develop a propositional framework that helps to explain the likely impact of such capabilities for characteristically different kinds of innovation projects at the micro level.