Background-Administrative data from medical claims are often used for injury surveillance. Effective October 1, 2015, hospitals covered by the Health Insurance Portability and Accountability Act were required to use the International Classification of Diseases, 10th Revision, Clinical Modification (ICD-10-CM) to report medical information in administrative data. In 2017, the National Center for Health Statistics (NCHS) and the National Center for Injury Prevention and Control (NCIPC) published a proposed ICD-10-CM surveillance case definition for injuryrelated emergency department (ED) visits. At the time, ICD-10-CM coded data were not available for testing. When data became available, NCHS and NCIPC collaborated with the Council of State and Territorial Epidemiologists and epidemiologists from state and local health departments to test and update the proposed definition. This report summarizes the results and presents the 2021 revised ICD-10-CM surveillance case definition.