The habitats listed in Annex I of the 1992 European Union Directive on the conservation of natural habitats and of wild fauna and flora cover a wide range of both terrestrial and marine habitats, including a large number that are semi natural rather than natural. Implementing the directive has revealed many problems, particularly with identifying the habitats in the field and the absence of information on habitat distribution. As a result the Directive has been responsible for much survey work and has increased our knowledge of many habitats and species across the European Union. As data are reported to the European Commission in agreed standard formats, a database of information about habitats now exists that can be used for other projects. Monitoring obligations will give another unified source of information at a European Union scale.