Despite the fact that many early childhood initiatives depend on the collaboration of multiple organizations and stakeholders, little is known about what makes for successful collaboration within the field of early care and education. In May of 2010, a working meeting was convened by the Office of Planning, Research and Evaluation to begin to address this issue. This brief builds on work that began during that meeting and extended in the years that followed, particularly work identifying the key components of collaborations and developing a logic model for measuring collaboration in an early childhood context. The first section of this brief presents the logic model, explains its core components, and highlights these components by mapping them onto a hypothetical example of collaboration in early care and education. The next section of the brief shares the results from an extensive review of existing measures of collaboration. Thirty-two measures were found. The last section of the brief describes key measurement considerations and offers some discussion of future directions for collaboration research in the field of early care and education. (author abstract)