This paper provides an analysis of the impact of patent fees on the demand for patents. It presents a dataset of fees since 1980 at the European (EPO), the US and the Japanese patent offices. Descriptive statistics show that fees have severely decreased at the EPO over the 1990s, converging towards the level of fees in the US and Japan. The estimation of dynamic panel data models suggests that the price elasticity of demand for patents is about -0.30. These results suggest that the laxity of fee policy at the EPO has significantly contributed to the rising propensity to patent. © Blackwell Publishing Ltd and the Department of Economics, University of Oxford, 2011.