This study relates differential socioeconomic status between blacks and whites to racial differentiation in infant mortality rates. The basic assumption is that decreases in socioeconomic differentiation and related variables lead to decreases in the black—white infant mortality differential. A comparative approach based on aggregate measures of socioeconomic differentiation is utilized to compare sixty-one United States urban places. Path analysis shows that neonatal mortality differentiation is virtually unaffected by socioeconomic differentials while decreased racial differences in hospital births tend to increase neonatal mortality differentiation. In contrast, postneonatal differentiation is affected by socioeconomic differentiation, especially along the dimensions of income, education, and regional location. It is concluded that despite some suggestions that infant mortality is no longer responsive to socioeconomic factors, postneonatal differentation is affected by socioeconomic differentials when comparison is based on city units.