First, the current guideline reflects numerous innova- tions and modifications that were incorporated into the AHA clinical practice guideline format. Introduced in 2017, modifications to AHA guidelines included making the text shorter and more user friendly; focusing guide- lines on recommendations and patient management flow diagrams and less on extensive text and back- ground information; formatting guidelines so that they can be easily updated with guideline focused updates; and including chunks of information after each rec- Second, the Diagnostic Evaluation and Systems of Care for Secondary Prevention sections are new. The Diagnostic Evaluation for Secondary Stroke Prevention section focuses on the evidence base for laboratory and imaging studies for guiding secondary stroke prevention decisions. Often these tests are com- pleted in the inpatient setting. The Systems of Care for Secondary Prevention section contains 3 subsections: (1) Health Systems Based Interventions for Secondary Stroke Prevention, (2) Interventions Aimed at Chang- ing Patient Behavior, and (3) Health Equity. The Health Equity subsection is a refocus of the 2014 guideline s section guiding management of high-risk populations. Third, this guideline does not include a separate section on metabolic syndrome because there are no unique recommendations for metabolic syndrome aside from managing each of the individual components of the syn- drome. Fourth, the section on alcohol use was expanded to include the use of other substances. Finally, several additional conditions were included in the Management by Etiology section: congenital heart disease, cardiac tumors, moyamoya disease, migraine, malignancy, vas- culitis, other genetic disorders, carotid web, fibromus- cular dysplasia, dolichoectasia, and embolic stroke of undetermined source (ESUS). In developing the 2021 secondary stroke prevention guideline, the writing group reviewed prior published AHA/ASA guidelines and scientific statements. 