A theoretical and widely-quoted finding is that levels of cooperative R&D exceed noncooperative R&D levels when technological spillovers are relatively large, while the opposite holds for relatively small technological spillovers. We qualify this result by showing that for relatively small technological spillovers the comparison is not driven by the extent of technological spillover, but by the increase in technological spillover due to cooperation in R&D. In particular, an agreement to cooperate in R&D always raises R&D efforts if the post-cooperative technological spillover rate is “high enough”.