This third edition of ‘Controversies’ recapitulates the last edition with a topic that again includes a discussion of trial design and ethics, technical expertise, reimbursement and generalization of study data within a heterogeneous population. The evidence for the intra-arterial therapy for acute ischemic stroke is the subject of this edition; the authors are two influential leaders in the field of neurology and cerebrovascular disease who have been at the forefront of the field for decades and whose research has directly shaped the direction of national clinical trials. Dr William Powers succinctly analyzes the trial data available for intra-arterial stroke therapy and its limitations, including the dangers of using historical controls and surrogate endpoints. He elaborates on the difficulty in selecting patients for whom the benefit will outweigh the risk in the absence of robust clinical trial data and, furthermore, how this ‘missing link’ argues against the proclamation that providing intra-arterial therapy for acute ischemic stroke is an indicator of improved quality of care. Dr Anthony Furlan recognizes that the …