The Study of Early Head Start-Child Care Partnerships defines partnerships as formal arrangements between Early Head Start programs and community child care providers to provide services to eligible families with infants and toddlers. Services provided in child care settings should comply with the Head Start Program Performance Standards (HSPPS). Partnership services are usually funded through a combination of Early Head Start grant funds and child care subsidies. The purpose of Early Head Start-child care partnerships is to provide coordinated, high quality, comprehensive services to low-income infants and toddlers and their families. Achieving this goal requires contributions from Early Head Start programs; child care providers (including family child care homes and child care centers); families; and systems partners operating at the national, state, and local levels, such as child care subsidy systems, quality rating and improvement systems (QRISs), and federal technical assistance systems. The draft theory of change visually represents these four types of partners as puzzle pieces to acknowledge that all partners need to work together in a coordinated manner to achieve results. Together, these groups invest inputs and carry out activities designed to lead to five long-term outcomes: (1) sustained, mutually respectful, and collaborative, Early Head Start-child care partnerships; (2) increased community supply of high quality infant-toddler care; (3) improved family well-being; (4) improved child well-being and school readiness; and (5) well-aligned infant-toddler policies, regulations, and quality improvement supports at the national, state, and local levels. The theory of change also notes a range of organizational and contextual factors that are likely to influence partnerships. In the theory of change and throughout this document we use the term partnership programs to refer to programs (including Early Head Start programs and child care providers) funded under the new Early Head Start-child care partnerships initiative. The theory of change represents a comprehensive and broad range of inputs, activities, short- and long-term outcomes, and organizational and contextual factors that could be associated with Early Head Start-child care partnerships. However, not all partnerships will include all inputs, perform all activities, aim to achieve all outcomes, or involve all of the organizational and contextual factors included in the theory of change. (author abstract)