Healthcare outcomes such as overall survival or quality of life are the end results of a complex interaction between the patient, treatment and the healthcare system. Research may identify superior interventions but their dissemination and changing the behaviour of healthcare providers is challenging. Demonstrating and measuring the benefits of clinical research on healthcare outcomes is an important issue but there is remarkably little empiric work to date in this area. In this chapter we explore benefits that may arise in healthcare from contributing to clinical research, and consider the mechanisms which may be relevant. Improvements in infrastructure, the processes of care and workforces are important. Complex adaptive systems theory provides a framework for considering the many feedback loops that relate research, health outcomes and the behaviour of healthcare providers. Given the costs of research, additional studies to examine the impact of research on healthcare outcomes and to explore the mechanisms are justified and highly desirable.