In all developed countries, single-parent families are particularly vulnerable to poverty. In contrast to many European countries that provide some guaranteed income support for children, the United States has emphasized private responsibility, increasingly requiring child support from the other parent. The reliance on a private approach raises several questions concerning the adequacy and distribution of child support. Using detailed administrative records for virtually all mothers with new child support orders in one U.S. state in 2000, we analyze child support receipts over the subsequent three years. We find that most mothers with child support orders receive support, and many receive substantial amounts. However, the amount received varies substantially from year to year. Moreover, we find substantial instability within years--a characteristic of private support that has been difficult to measure with prior data. Our analysis of child support outcomes across the income distribution shows remarkably similar proportions of families receiving at least some support. Considering amounts received over the distribution of pre-child-support income, we find a U-shaped pattern, with amounts declining slightly with income over the first three deciles, and then increasing steadily. Lower-income families are also less likely to receive regular child support. Nonetheless, child support plays an important role in the income packages of many low-income families, reducing pre-child-support poverty rates by 16 percent and closing the poverty gap by an average of 44 percent in 2001.