This study investigates causes of black residential segregation. The units of analysis are cities and a causal model is specified and evaluated using the technique of path analysis. The principal hypotheses are supported, although there is some interaction with regional location. The data suggest that the relative status of blacks and black population size are important determinants of segregation; these findings are especially interesting given the general belief that black socioeconomic progress is unrelated to changes in segregation, as well as the tendency to ignore absolute size of the black population in analyses of segregation. Also important are percent black and the relative growth rates of the white and black populations; however, the impact of the latter variable was smaller than anticipated in view of the emphasis often given to it.