ABSTRACT. Although residential concentrations of immigrant ethnic groups in cities were common a century ago, it is not clear to what extent members of more recently arrived groups live near each other. We attempt to determine how common such clustered settlement is today, using 2000 census data to measure concentrations of Asians, Hispanics, and their larger ethnic subgroups in fifteen large metropolitan areas. The percentage of an ethnic group that is residentially concentrated correlated significantly with the group's proportion in an area. With metropolitan areas weighted equally, 38 percent of Hispanics and 13 percent of Asians were concentrated. However, when we analyzed eight specific nationality groups, the residentially concentrated proportion ranged from 14 to 59 percent. Level of cultural assimilation appears to explain group differences in level of concentration. Although ethnic concentrations were more pronounced in the largest metropolitan areas, important concentrations were also found in many of the smaller areas in our study.