This ebook focuses on research about adaptation and fidelity in health education. Fidelity refers to following prescribed methods and delivering the messages that are prescribed by the programme. Adaptation on the other hand implies that something about a health education programme, either a method or a message, was changed when it was implemented. As educational programmes are adopted and delivered in schools or community settings, the ever-present goal is to improve health behaviours. Fidelity and adaptation may both affect outcomes. Common sense and empirical research align to suggest that the respective impacts of fidelity and adaptation are important to understand in order to improve the ability of practitioners to achieve programme goals.