National surveys of R&D labs across the manufacturing sectors in the US and Japan show that intraindustry R&D knowledge flows and spillovers are greater in Japan than in the US and the appropriability of rents due to innovation less. Patents in particular are observed to play a more central role in diffusing information across rivals in Japan, and appear to be a key reason for greater intraindustry R&D spillovers there, suggesting that patent policy can importantly affect information flows. Uses of patents differ between the two nations, with strategic uses of patents, particularly for negotiations, being more common in Japan. © 2002 Elsevier Science B.V. All rights reserved.