The research concerned the interrelations among several indexes of residential segregation and measures of educational, occupational, and income differentiation in American urban areas as of 1960. The exploratory hypothesis was that differences in reported findings result, in large part, from methodological variations. Specifically, they are due to differences in the census unit (i.e., central city versus SMSA), and in the index areal unit (i.e., block versus tract). The analysis (1) lent strong support to this hypothesis and (2) questions the accuracy and comparability of substantive interrelations in the presence of measurement error.