The first of two volumes in the Advances in Child Development and Behavior series, Equity and Justice in Developmental Science: Theoretical and Methodological Issues focuses on conceptual issues, definitions, and critical concepts relevant to equity and justice for the developmental sciences. This volume covers critical methodological issues that serve to either challenge or advance our understanding of, and ability to promote, equity and justice in the developmental sciences. Both volumes bring together a growing body of developmental scholarship that addresses how issues relevant to equity and justice (or their opposites) affect development and developmental outcomes, as well as scholarship focused on mitigating the developmental consequences of inequity, inequality, and injustice for young people, families, and communities and ensuring that all young people have opportunities to develop and thrive.