This study focuses on rural development policy implementers and evaluators as users of European biodiversity data. It critically analyses the use of biodiversity data for measuring the impact of agri-environment programmes and related rural development funding, and highlights good practices from a range of countries. The examples show the possibilities for better targeting and evaluation of agricultural funding to biodiversity conservation if sufficient biodiversity data are available and are used in policy. However, many biodiversity datasets exist at the national or regional but are still not integrated in the RDP monitoring system and thus not accessible to evaluators, and many RDPs still feature only the obligatory EU-level indicators. It is important to differentiate between the need for standardised EU-level datasets that can be used for an overall assessment of the impact of the CAP, where there is still a huge data gap, and the national or regional programming level, where there are often existing data that are not being used for various reasons. The study is part of the EU BON project, which aimed to build an integrated biodiversity information system for Europe.