The EMCDDA Trendspotter case study on Fentanyl in Europe was undertaken during September and October 2012. It culminated in an expert meeting in Lisbon on 9–10 October 2012. The aim of the study was to increase understanding of the availability and illicit use of fentanyl in Europe, with a specific focus on: the extent and patterns of use; illicit production and diversion; harms and deaths; and, responses to the problem. Twelve experts from 10 EU Member States (Bulgaria, Czech Republic, Germany, Estonia, Greece, Italy, Slovakia, Sweden, Finland, United Kingdom) attended the meeting, presenting their experiences and contributing to an analysis of the topic, providing insights from law enforcement, forensics, treatment, research and monitoring, and drug user perspectives.