Appropriate assessment is a mechanism to ensure protection of Natura 2000 from harmful human activities, especially construction plans and projects. If a plan may have significant adverse effects on the site, measures to prevent those effects will be sought. Without appropriate assessment, the project or plan cannot be authorised. Appropriate assessment is regulated in Article 6 of the EU ‘Habitats’ Directive. But there’s more than meets the eye: the Court of Justice of EU has further specified the rules in numerous cases. In this introduction, prepared with the support of the Central European Initiative, you can read about the basics of this legal instrument.