Facing mounting evidence that California has fallen behind on many key indicators of educational performance, policymakers and the public share considerable interest in exploring whether California should expand public funding for preschool education. This expanded funding will be most effective if resources can be directed to their most efficient uses. Doing so requires an understanding of how resources are currently allocated, what educational objectives preschool education can help achieve, and where preschool resources can be most effective. To investigate these issues, the RAND Corporation undertook a multicomponent study called the California Preschool Study to examine the adequacy and efficiency of preschool education in California. Researchers completed three studies to advance knowledge of (1) gaps in school readiness and achievement in the early grades among California children and the potential for high-quality preschool programs to close existing gaps, (2) the use of early care and education (ECE) services among California's children and the quality of those experiences, and (3) the system of publicly funded ECE programs in California in the two years before kindergarten entry. The objective of this analysis, the fourth and final study component, is to integrate the results from the series of studies, as well as relevant prior research, and make recommendations to advance preschool adequacy and efficiency in California. Five chapters comprise this monograph. Following an introduction, Chapter One addresses the author's first three research questions regarding adequacy and efficiency of preschool education in California: the size of achievement gaps in the early elementary grades and the potential for preschool to narrow existing gaps; the extent to which preschool-age children in California participate in early-learning programs and the quality of the settings they are in; and the features of the existing system of publicly funded ECE programs for preschool-age children in California and the potential for efficiency gains in a modified system. The answers to these questions derive from the findings gleaned from the three focused studies that preceded this monograph. Chapter Three addresses the author's fourth research question by examining the advantages and disadvantages of various design options for specifying preschool access, providing program services, ensuring high quality, and promoting efficiency through other aspects of program infrastructure. In some cases, there is no clear research basis for adopting one policy approach or another, and it will be up to policymakers and the public to express their preferences based on how they weigh the advantages and disadvantages of various options. In other cases, a stronger argument can be made for one approach over another. To complete the answer to the fourth research question, this report draws on the design considerations to offer a series of recommendations, outlined in Chapter Four, for improving the adequacy and efficiency of preschool education in California. The specific recommendations for policy action include those that are possible with existing resources as well as those that are possible only by making more resources available. Chapter Five summarizes what we have learned about preschool adequacy and efficiency in California and highlights both policy considerations associated with advancing preschool adequacy and efficiency and the cumulative set of recommendations. Broader implications of the recommendations are also discussed. (Contains 62 footnotes, 12 figures, and 22 tables.) [Additional funding was provided by the National Institute for Early Education Research and Los Angeles Universal Preschool.]