This executive summary of the final report of the National Day Care Study (NDCS) of March 1979 summarizes findings and policy recommendations, gives the background to the study and presents findings on quality and costs of center-based day care. Recommendations for federal regulations for preschool children, infants and toddlers, center characteristics, regulatory language and monitoring guidelines are indicated. The major cost/effects study of center-based day care for preschool children was conducted between 1974 and 1978 in 67 day care centers in Atlanta, Detroit and Seattle. Data from the major study and two supporting studies, a smaller research effort focusing on center day care for infants and toddlers and a national telephone survey of 3100 randomly selected centers, were analyzed. The NDCS found that higher quality care is associated with two low-cost ingredients (smaller groups of children and caregivers with child-specific education/training). The number of classroom staff per group (caregiver/child ratio) was not an important contributor to quality within the policy-relevant range of 1:5 to 1:10. Ratio was strongly related to differences in cost. Regulatory language and rules used to monitor compliance were found to influence center practices as much as the content of the regulations. The study concluded that revision of current federal day care regulations could allow the government to buy better care at slightly lower cost. More children could be better served within current budgets. (Author/RH)