The aim of this paper is twofold. In the first part a comparative analysis of the main tendencies of R&D expenditure and patenting activity in a sample of OECD countries is done for the period 1981-99. In the second an econometric analysis is performed in order to estimate the effects of the R&D carried out by different institutional actors such as firms, government and university on patenting activity. The main results are the following. Firms R&D expenditure steadily increased during the period under examination, while public funding shows a decreasing trend in the Nineties. These different dynamics negatively affected the share of R&D expenditure allocated to the high-tech sectors. There is no evidence of a long run tendency of decreasing returns to R&D. A weak and discontinuous convergence process is at work in terms of R&D/PIL ratio, while no clear convergence or divergence tendency can be detected with regard to patents. The econometric analysis shows that firms and government R&D affects positively patenting activity, surprisingly that does not hold for university research.