This research letter examines the frequency of discordant documentation of patient race and ethnicity in emergency department (ED) visits. The study analyzed data from a statewide, multicenter registry of ED visits in Michigan, covering 42 hospitals across 10 health systems from December 1, 2018, to November 30, 2021. The study focused on patients with at least two ED visits to the same hospital or health system. Race and ethnicity data were combined into a composite variable, including categories such as American Indian or Alaska Native, Asian or Pacific Islander, Hispanic, non-Hispanic Black, non-Hispanic White, multiracial, and other. The primary outcome was the frequency of discordant documentation of race and ethnicity between ED visits. The study found that 1.7% of adults and 7.0% of children had discordant racial and ethnic data across visits. Among adults, Black and other categories accounted for the largest proportions of discordant documentation, while among children, White, multiracial, and other categories were most common. The findings highlight significant variability in the documentation of race and ethnicity, which may affect measurement, resource distribution, predictive modeling, policy, and reimbursement. The study emphasizes the need for increased investment in outlining best practices for primary data collection, particularly in the ED. Limitations include reliance on health system record numbers, variability in data collection practices, and limited description of the "other" category. The study was deemed exempt by the University of Michigan Institutional Review Board as it is secondary research and followed the STROBE reporting guideline. The research was supported by Blue Cross Blue Shield of Michigan and Blue Care Network as part of the BCBSM Value Partnerships program. No funding was obtained for the work presented. The findings suggest variability and inconsistency in the approach to assigning race and ethnicity, given the focus on repeat ED visits to the same hospital or health care system.This research letter examines the frequency of discordant documentation of patient race and ethnicity in emergency department (ED) visits. The study analyzed data from a statewide, multicenter registry of ED visits in Michigan, covering 42 hospitals across 10 health systems from December 1, 2018, to November 30, 2021. The study focused on patients with at least two ED visits to the same hospital or health system. Race and ethnicity data were combined into a composite variable, including categories such as American Indian or Alaska Native, Asian or Pacific Islander, Hispanic, non-Hispanic Black, non-Hispanic White, multiracial, and other. The primary outcome was the frequency of discordant documentation of race and ethnicity between ED visits. The study found that 1.7% of adults and 7.0% of children had discordant racial and ethnic data across visits. Among adults, Black and other categories accounted for the largest proportions of discordant documentation, while among children, White, multiracial, and other categories were most common. The findings highlight significant variability in the documentation of race and ethnicity, which may affect measurement, resource distribution, predictive modeling, policy, and reimbursement. The study emphasizes the need for increased investment in outlining best practices for primary data collection, particularly in the ED. Limitations include reliance on health system record numbers, variability in data collection practices, and limited description of the "other" category. The study was deemed exempt by the University of Michigan Institutional Review Board as it is secondary research and followed the STROBE reporting guideline. The research was supported by Blue Cross Blue Shield of Michigan and Blue Care Network as part of the BCBSM Value Partnerships program. No funding was obtained for the work presented. The findings suggest variability and inconsistency in the approach to assigning race and ethnicity, given the focus on repeat ED visits to the same hospital or health care system.