This brief is part of a series that explores key implementation considerations important to consider when replicating evidence-based programs for children and youth. It focuses on the importance of identifying, operationalizing, and implementing the “core components” of evidence-based and evidence-informed interventions that likely are critical to producing positive outcomes. The brief offers a definition of “core components,” discusses challenges and processes related to identifying and validating them, highlights rationales for the importance of operationalizing core components, and explores implications for selecting, funding, implementing, scaling up, and evaluating programs. This is one of four research briefs prepared under the auspices of an ASPE contract entitled Emphasizing Evidence-Based Programs for Children and Youth: An Examination of Policy Issues and Practice Dilemmas Across Federal Initiatives.