Adolescent risk-taking behaviour has potentially serious injury consequences and school-based behaviour change programmes provide potential for reducing such harm. A well-designed programme is likely to be theory-based and ecologically valid; however, it is rare that the operationalisation process of theories is described. The aim of this paper is to outline how the theory of planned behaviour and cognitive behavioural therapy informed intervention design in a school setting. Teacher interviews provided insights into strategies that might be implemented within the curriculum and (...) provided detail used to operationalise theory constructs. Benefits and challenges in applying both theories are described with examples from an injury prevention programme, Skills for Preventing Injury in Youth. (shrink)