In this chapter we explore the reasons why health researchers are increasingly expected to engage with the public in their research. By the end of the chapter you should: understand key concepts and principles associated with public engagement; be confident in how to go about developing a plan to engage members of the public in your research project; be able to recognize some of the practical, ethical and methodological challenges of undertaking public engagement; and be aware of the possible impacts on research and for people involved that are associated with engagement and how to go about measuring these.