This book is available in Open Access format under a CC BY 4.0 license. It presents the results of a comprehensive comparative study on the implementation of the EU Directive on pharmacovigilance in six EU member states. By going beyond legal implementation and focusing instead on practical implementation, this study aims to fill a gap in EU compliance research. Based on qualitative interviews with relevant stakeholders in Germany, Poland, Portugal, France, Finland, and the United Kingdom, the authors identify perceived challenges and best practices, provide recommendations, and contribute to a better understanding of the factors that promote or hinder the practical implementation of EU law at the national level.