Using the 1960 Census Tract data for Philadelphia, we examine the degree of residential congregation and segregation of the six principal “national origin” groups in the city, relating the patterns of congregation and segregation in turn to a variety of socioeconomic characteristics of the tracts. The intercorrelation matrix of these national origin groups forms a Guttman simplex with several interesting “inversions” that, in turn, predict “inversions” on selected socioeconomic characteristics of the tracts. In a technical appendix, we consider the relative merits of the Duncan index of dissimilarity and our use ofphicorrelation coefficients for the purposes of our particular problem.