The term "underclass" is often used to describe concentrations of inner-city Blacks in urban neighborhoods where social problems are common, mostly in large metropolitan areas. The most widely used empirical measurements of underclass are the spatial concentrations of poverty and social problems. Characterizing the underclass as almost entirely a minority problem may result from focusing on large metropolitan areas. There is uncertainty about the actual racial and ethnic compositions of the underclass. Analyzing differences in the spatial concentrations of poverty and social problems in small, middle-sized, and large metropolitan areas, and separating Hispanic Americans, non-Hispanic Blacks, and non-Hispanic Whites reveals the composition of the underclass more accurately. Data are analyzed from the Urban Institute Underclass Data Base, which contains tabulations from over 42,000 tracts from the 1980 census and over 34,000 in the 1970 census. As the size of the metropolitan area falls, the Black share of population in underclass neighborhoods falls, but the White and Hispanic American shares rise. If one looks beyond Chicago, New York, and Los Angeles, underclass neighborhoods are most likely to be populated by Blacks, then Whites, and then Hispanic Americans. By ignoring small and middle-sized metropolitan areas, scholars and journalists have ignored the White underclass. Statistical data are provided in 12 tables. There are 25 references. (SLD)