An emerging hypothesis about black progress since the civil rights movement in the United States postulates that economic polarization is occurring in the black community. This hypothesis, which incorporates conflicting earlier theories of declining versus persistent racial differences, suggests that talented and well-educated blacks are competing successfully with whites, while other blacks are falling further behind both whites and successful blacks, and that the gap between those at the top and those at the bottom of the economic structure is widening. To test the polarization hypothesis, socioeconomic data on blacks and whites were analyzed. The analysis produced mixed results. Data on occupational prestige distributions and proportions of labor force nonparticipants suggested that polarization may be occurring. On the other hand, data on educational attainment distributions and earnings/employment returns to education indicated that the black community is becoming more homogeneous. Analysis of family income according to degree of concentration among income groups refuted the polarization hypothesis, while findings of a widening dollar gap between rich and poor supported the hypothesis. Finally, data on economic differentials by type of family clearly supported the hypothesis of polarization. (Author/MJL)