We examine the dynamics of knowledge production for a panel of 19 OECD countries. A new and unique data set is used to proxy the domestic flows of “new-to-the-world” knowledge and ideas. We rigorously address the cross-country heterogeneity in the production of knowledge and the endogeneous nature of this process. The parameters of the knowledge production function point to large cross-country differences. Domestic and foreign stocks of knowledge and ideas have a net positive effect on the production (flows) of new ideas. Countries with a low domestic knowledge base appear to improve their TFP considerably through the accumulation of knowledge. This effect is very modest for countries that already have a sizeable domestic knowledge base. We find ample evidence of duplicate R&D but no support for endogenous growth. Given the heterogeneous nature of knowledge production across OECD countries, R&D policy will need to be adapted to the specific nature of each country; a one-size-fits-all approach will not be effective.