This project aims at analysing the complementarity of investment in patents and trademarks for firm performance by employing an extensive data set of European firms. Patents and trademarks are both intellectual property rights (IPRs) that can be used to secure returns on investment for different types of innovation activities. While patents focus on the protection of investment in technological knowledge (i.e. the results of R&D), trademarks are typically used to safeguard returns from marketing investment in new products and branding activities such as advertising. Since resources are scarce, firms will have to decide on the scale of their R&D and marketing investment for building up patent and trademark portfolios. The main research question of the project investigates whether strong in investment in both types of IPRs yield higher performance effects than a strategy that focuses on only one of the two types.The empirical analysis rests on a panel data set of nearly 1,000 firms from Europe which covers the period from the 1992 to 2012. The data are taken from the R&D Scoreboard of the European Commission and a predecessor project by the former UK Department of Trade and Industry. Firm data are merged with data on patent applications and grants from the European Patent Office (EPO) and data on trademark registrations at the Office for Harmonization in the Internal Market (OHIM), which is responsible for registration of trademarks and designs in the EU countries, in order to establish a firm-specific stock of patents and trademarks. By using panel regressions, we analyse the impact of patent stock and trademark stock, as well as other tangible and intangible assets, on firm performance, considering different firm performance measures (total factor productivity and profitability). The results of this project will contribute to a better understanding of the role of trademarks as a specific form of investment in intangible assets.