Working in accordance with the evidence model is challenging, which prompted research interest in identifying barriers to implementing evidence-based interventions, programmes, services and other practices to achieve an evidence-based practice. Studies of the determinants of implementation led to research on implementation strategies for overcoming barriers and harnessing facilitators. This chapter provides a historical background to implementation science, focusing on the evidence-based movement but also addressing other research that has influenced implementation science, including research on the spread of innovations, the utilization of research-based knowledge in healthcare practice and policy implementation. © 2024 selection and editorial matter, Per Nilsen; individual chapters, the contributors.