The concept of family-centered care was introduced to the public more than 4 decades ago, stressing the importance of the family in children's well being. Since then, family-centered values and practices have been widely implemented in child health. The purpose of this article is to offer an overview of the development and evolution of family-centered theory as an underlying conceptual foundation for contemporary health services. The focus includes key concepts, accepted definitions, barriers, and supports that can influence successful implementation, and discussion of the valid quantitative measures of family-centeredness currently available to evaluate service delivery. The article also provides the foundation, and proposes questions, for future research.