In a sample of Detroit-area mothers of preschool-aged children interviewed in 1986, one-third reported that child care problems had constrained their employment. Such reports were relatively prevalent among poor women, those without relatives nearby, and those willing to entrust the care of their children to nonfamily members. Only one-tenth of the sample reported a similar child care constraint on fertility, a phenomenon unrelated to income but relatively prevalent among women with strong labor force attachment. The results suggest that policies to increase the supply of child care or to lower its cost could increase female labor supply by a substantial fraction, with an even greater rise among women most at risk of poverty and reliance on public assistance, but probably would not raise fertility significantly.