The purpose of the paper is to advance the scholarly understanding of how different combinations of proximities in collaborative R&D projects drive radical innovation. We use fuzzy set Qualitative Comparative Analysis to explore how configurations of geographical, cognitive, social and institutional proximity lead to radical innovations in collaborative R&D projects. The analysis generates three solutions. Each solution includes either cognitive, organizational or geographical distance, and all include social proximity. Thus, our results indicate that social proximity is central but not sufficient for radical innovation in R&D projects as it must be combined with a distance in another dimension. This shows that even though distance is a necessity to achieve radical innovation it seems difficult to cope with distance in more than one dimension at a time. The results contribute to novel insights in an area where previous research has generated contradictory and ambiguous results.