Disaggregate panel data estimates are presented of equations that relate a set of OECD countries' sectoral total factor productivity to domestic and to foreign R&D capital. The estimates indicate that there are both important international and national R&D knowledge spillovers and that these spillovers are intersectoral and intrasectoral in nature. They show that the influence of domestic R&D is stronger in the large economies and that this is caused by more important domestic intersectoral R&D spillovers. There is also evidence of a greater influence of domestic and of foreign R&D in research intensive industries and of an interaction between the domestic economy scale and the research intensity effects.