Objective: The dynamics of interactions between evidence-based intervention (EBI) developers and trainers and organizations and providers that deliver the EBI was examined in two case studies, a statewide randomized effectiveness trial of an EBI to reduce child neglect and a randomized trial of EBIs for depression, anxiety, and conduct problems in children and adolescents. Methods: Data were collected using ethnographic methods of participant observation and semistructured interviews and analyzed using grounded theory analytic methods. Results: Formal and informal interactions between EBI propagators and end users provide access to resources and exchange of global and local knowledge of service delivery. Productive interactions require accessibility, mutual respect, a shared language, and a willingness to engage in negotiation and compromise to resolve differences in demands imposed by organizational culture, the need for EBI fidelity, and client characteristics. Conclusion: A cultural exchange characterized by information sharing and behavioral change through a process of negotiation and compromise is central to evidence-based practice in youth serving systems of care.