The theoretical and empirical implications of the structural basis of panethnicity and of the layering of ethnic boundaries in residential patterns are considered while simultaneously evaluating the "panethnic hypothesis," the extent to which homogeneity within panethnic categories can be assumed. Results show a panethnic effect--greater residential proximity within panethnic boundaries than between, net of ethnic group size and metropolitan area--that is dependent on immigration. A lower degree of social distance between panethnic subgroups is observed for blacks, whites, and Latinos, and less for Asians, yet ethnonational groups continue to maintain some degree of distinctiveness within a racialized context.