A summary of the proceedings of a meeting hosted by the Office of Planning, Research and Evaluation, Administration for Children and Families, in Silver Spring, MD on September 21-22, 2010, for the purpose of clarifying the definitions and key concepts used in implementation science, exploring the potential lessons learned from applying implementation science principles in early care and education research and evaluation, and identifying products that will assist policymakers and early childhood researchers in applying implementation principles within their research and evaluation work