In the United States, interest in early childhood development has grown dramatically over the past two decades and continues to expand. Increasing public support for programs and services that address the needs of young children and their families provides numerous opportunities for social work intervention. This article describes three major early childhood systems--early intervention, Early Head Start, and early care and education--and discusses ways that social workers can strengthen programs within these systems and improve outcomes for participating children and families. Social workers' understanding of and commitment to family-centered practice and cultural competence are highlighted. Opportunities for social workers to become involved in advocating for, developing, and leading high-quality early childhood programs and implications for social work education are also discussed.