The compliance cost that environmental regulation imposes on businesses plays a central role in the debate on economic competitiveness and environmental sustainability. However, on closer inspection these costs often turn out to be lower than originally anticipated. As part of a a European consortium, Ecologic reviewed ex-post analyses of the costs imposed on business because of European environmental legislation, and compared these to ex-ante estimates. The project reports conclude that some ex-ante overestimation is inevitable, and that the new EU regulatory flexibility could make accurate predictions even more difficult. But it nevertheless proposes a series of ways in which accuracy could be improved.