For the first time in this century, Black women are participating in the labor force at lower rates than are White women. The Black-White gap in female labor force participation is driven by those in the severest need of income-women heading households. I compare three explanations of the Black-White gap in labor force participation among female household heads-lack of human capital, lack of opportunities resulting from industrial restructuring, and disarticulation from mainstream institutions as described by theories of the "underclass." Using a representative national sample from the Panel Study of Income Dynamics, I find that lower rates of labor force participation among Black women heading households are determined by Black-White differences in human capital as well as by characteristics associated with a breakdown in the processes linking Black women to the labor market. Overall, the largest impediments to labor force participation among women heading households are dropping out of high school, having a child under the age of six in the household, and being a long-term welfare recipient.