Mark Freedman, MSc, MD, CSPQ, FAAN, FRCPC, University of Ottawa & Ottawa Hospital Research Institute, Ottawa, Canada, discusses the common occurrence of cognitive fatigability in patients with multiple sclerosis (MS). Defined as an inability to maintain performance throughout a sustained cognitive task, cognitive fatigability is seen more frequently in patients with MS than healthy controls. Effectively assessing cognitive deficits in MS to detect and quantify cognitive fatigability is an area of ongoing research and could help to determine treatment strategies in the future. This interview took place during the ACTRIMS Forum 2021.