This paper studies the endogenous formation of R& networks among upstream firms and the welfare implications thereof. Both under an upstream price setting and an upstream quantity setting, it is shown that the complete R& network emerges in equilibrium but only if spillovers are sufficiently low. Yet, under a quantity setting, the complete network arises within a larger range of spillovers. In both cases, however, there is a potential conflict between private incentives for R& collaboration and societal ones. We discuss policy measures that may help to steer firms towards a more socially desirable outcome.