Guiding principles for using sliding fee scales are presented in this paper in an effort to help states plan new child care initiatives, coordinate or strengthen existing programs, and improve sliding fee scales for current programs. Introductory comments urge states to adopt a single sliding fee scale for all their child care programs. The report then discusses the benefits of good sliding fee scales for children, parents, providers, and states. The Children's Defense Fund (CDF) model for sliding scales is discussed next. This model calls for: (1) fully subsidized care, with no copayment, for families with incomes less than 34% of the state median income (SMI) whenever possible; (2) the gradual increase of copayments from 0% to 8.2% of income for families with incomes between 34% and 75% of SMI with only 1 child in care; (3) the increase of copayments by 25% for families with 2 or more children in care, with copayments gradually rising from 0 to 10.3% of income for families with incomes between 34% and 75% of SMI; (4) gradual increases in the copayment as income rises; and (5) the creation of a sliding scale for families with school-age children in part-time care. Guidelines for determining family size and income, certifying eligibility and copayments, and family income reporting are presented. The final section discusses questions related to fee exemptions for poor families, the income level at which parents should absorb full child care costs, and guidelines for children in protective services. The bulk of the report consists of charts showing family copayments under the CDF model, depending on income, family size, and state of residence. (AC)