Simona Sacco, MD, University of L’Aquila, L’Aquila, Italy, describes the development of the European Headache Federation (EHF) consensus on the definition of resistant and refractory migraine. The Delphi method was used, and several rounds of questions were assigned to the panel members. After each round, the answers were sent to the facilitator, who collected all answers and issued a report with comments and agreement rates. Using the results of the Delphi questions, a step-by-step approach was used to build the definitions. This interview took place during the International Headache Congress 2021.