This paper analyses the role of patent-filing fees requested by the member states of the European Patent Convention (EPC). We provide first empirical evidence showing that the fee elasticity of the demand for priority applications is negative and significant. Given the strong variation in absolute fees and in fees per capita across countries, this result indicates a suboptimal treatment of inventors across European countries and suggests that fees should be considered as an integral part of an intellectual property policy, especially in the current context of worrying backlogs. In addition, we show that the transfer rate of domestic priority filings to the European Patent Office (EPO) increases with the duration of membership to the EPO and the GDP per capita of a country, suggesting that member states experience a learning curve within the EPC. The high heterogeneity in the transfer rates casts some doubts on the practice that consists in relying on filings at the EPO or at the United States Patent and Trademark Office to assess the innovative performance of countries. © The Authors 2007. Published by Oxford University Press.