ObjectivesTo survey experts in Headache Medicine on their opinions regarding appropriate non-inferiority margins for outcomes commonly used in migraine research. MethodsMembers of the American Headache Society and the Canadian Headache Society were invited to participate in the Non-Inferiority Margins in Migraine Research (NIMM) survey. Adult and child neurologists with expertise in Headache Medicine were eligible to participate. The survey had a multiple choice format and comprised questions on respondent characteristics, eligibility, as well as expert opinion on non-inferiority margins for outcomes commonly used in trials of both prophylactic and acute interventions for migraine. ResultsNinety-nine eligible respondents completed the survey. Most respondents were adult neurologists (84.9%) and 74% reported practicing in the USA. The following were the most commonly selected non-inferiority margins: (1) change in monthly migraine attacks comparing baseline to the treatment period: 1 attack (39.4% selecting), (2) change in monthly migraine days comparing baseline to the treatment period: 1 day (44.4%), (3) change in average migraine intensity on a 4-point scale comparing baseline to the treatment period: 1.0 (31.3%), (4) percentage of participants who are pain-free 2 hours after the intervention: 5% (41.4%), (5) percentage of participants who have a migraine recurrence within 48 hours of treatment: 5% (42.4%), and (6) percentage of participants with sustained pain freedom: 5% (42.4%). ConclusionsThe results of the NIMM survey describe the opinions of a group of experts on appropriate non-inferiority margins for outcomes commonly used in migraine clinical trials. There was significant variability in responses and lack of consensus on the choice of non-inferiority margins. The survey did not incorporate the patient perspective and was not validated prior to distribution. Further work in this area is required in order to explore how to incorporate clinical considerations into the selection of non-inferiority margins for migraine research.