The Environmental Impact Assessment (EIA) Directive entered into force in 1985. Over its more than 20 year long existence, numerous projects in the EU Member States have been subject to the EIA procedure. To what extent the benefits of the EIA Directive outweigh its costs is largely unknown. Up to now, there has been no systematic evaluation of the costs and benefits of the EU’s EIA legislation and its implementation in the Member States. The projects aims therefore at calculating and systematically evaluating  the costs and benefits of the EIA Directive.