Outsiders’ views of a person’s race or Hispanic origin can affect how she sees herself, how she reports her race/ethnicity, and her social and economic experiences. Social processes of constructing race are complicated for people whose identity is not reflected back to them in interactions, and mismatched identification gives insight into social assumptions. Using unique linked data from the 2000 and 2010 censuses, we find that in 90% of our 3.7 million cases, proxy reports (e.g., neighbors) of a person’s race/ethnicity match responses given by the household. Match rates are high for non-Hispanic Whites, Blacks, and Asians and for Hispanic ethnicity. Matches are much less common for other groups (American Indian/Alaska Native, Pacific Islander, Some Other Race, multiracial, and the race(s) of Hispanics). Proxies often report biracial Black-Whites as Black, but tend to report biracial American Indian-Whites, Asian-Whites, and Pacific Islander-Whites as non-Hispanic White rather than as people of color. Proxies frequently report children as multiple race and elders as single race, whether they are or not, potentially lowering the average age of the multiracial population. Proxies tend to report the person’s race and Hispanic origin as consistent with others in the tract, potentially increasing measured residential segregation.