Background: Adults with severe challenging behaviour can achieve good "quality of life" outcomes in small supported accommodation services. Yet, the research indicates that they typically experience poorer outcomes than other adults with intellectual disability. This raises questions about the degree to which research has informed program design and implementation. Methodology: Data from an evaluation of a residential support service outlines a "program theory" for supporting people with intellectual disabilities and severe challenging behaviour. Results: One aspect of the "program theory," the "practice framework," which details how support staff should interact with service-users, is illustrated through documentary, observational and interview data. Conclusions: Policy and practice should be informed by the knowledge we have about what works. Describing a "program theory" demonstrates the utility of developing a "program theory" for human service organizations and underscores the value of practitioners being familiar with the findings of relevant, good-quality research.