We have restricted our recom- mendations to adults and to secondary prevention measures that are appropriately instituted within the first 2 weeks. We have not included recommendations for cerebral venous sinus thrombosis because these were covered in a 2011 scientific statement and there is no new evidence that would change those conclusions.2 An independent Evidence Review Committee was com- missioned to perform a systematic review of a limited number of clinical questions identified in conjunction with the writ- ing group, the results of which were considered by the writing group for incorporation into the 2018 Guidelines for the Early Management of Patients With Acute Ischemic Stroke (2018 and this 2019 update. The systematic reviews for the 2018 AIS Guidelines have been previously published.3,4 These guidelines use the American College of Cardiology (ACC)/AHA Class of Recommendations (COR) and Level of Evidence (LOE) format shown in Table 1. New or revised recom- mendations that supersede previous guideline recommendations are accompanied by 250-word knowledge bytes and data sup- plement tables summarizing the key studies supporting the rec- ommendations in place of extensive text. These data supplement tables can be found in Data Supplement 1 and literature search information for all data supplement tables can be found in Data Supplement 2. Because this guideline represents an update of the 2018AIS Guidelines, the term New Recommendation refers to recommendations that are new to either the 2018 AIS Guidelines or to this 2019 update. Existing recommendations that are un- changed are reiterated with reference to the previous publication. These previous publications and their abbreviations used in this document are listed in Table 2. When there is no new pertinent evidence for these unchanged recommendations, no knowledge byte or data supplement is provided. 