This report summarizes the findings of a literature review conducted as part of the Assessing the Implementation and Cost of High-Quality Early Care and Education (ECE-ICHQ) project. The project's goal is to create a technically sound and feasible instrument that will provide consistent, systematic measures of the implementation and costs of education and care in center-based settings that serve children from birth to age five. The ultimate measures will inform research, policy, and practice by improving understanding of variations in what centers do to support quality, their associated costs, and how resources for ECE may be better aligned with expectations for quality. The authors reviewed 49 studies and research syntheses in three areas--ECE quality, implementation science, and ECE costs--to create a conceptual framework that will guide measurement development. To begin to build measures of implementation and costs that can complement measures of quality, this literature review addresses four research questions: (1) What are the features of high quality ECE?; (2) What are the key implementation factors necessary to deliver high quality center-based ECE services?; (3) What factors directly contribute to increases or decreases in costs of providing high quality center-based ECE services?; and (4) What is the relationship between quality center-based ECE services and costs? The literature review revealed five primary findings: (1) Research reveals some associations between the features of an ECE center and quality, or children's outcomes, but the lack of clear evidence means that ECE-ICHQ data collection must start broad; (2) Little research has been done to reveal the associations between implementation factors, program features, and quality; (3) The state and community context can influence the implementation (and pursuit) of quality, as well as its cost; (4) Current measurement of the cost-to-quality relationship provides little direction for those who wish to invest in quality; and (5) The gaps in measurement identified in the literature review reveal the need to align measures of implementation and cost to inform the direction of any efforts to improve quality.