Researchers measure the effectiveness of new interventions using randomized controlled trials (RCTs). They are increasingly using qualitative research with these RCTs to explain the results of RCTs or facilitate the viability and efficiency of RCTs. is a "how-to" book about the use of qualitative research with RCTs. Divided into three parts, this book covers the process of using qualitative research with RCTs from start to finish. Section one outlines overarching issues such as the many contributions qualitative research can make to generating evidence of effectiveness, section two provides practical guidance from writing a proposal through to publishing qualitative research undertaken with RCTs, and the final section guides the reader on how to engage with relevant stakeholders. Each chapter focuses on the key steps of undertaking qualitative research in RCTs, giving examples of how to write a proposal, select research questions, integrate qualitative and quantitative components, and much more. is ideal for researchers who are leading, undertaking, or planning to use qualitative research with RCTs. With its detailed explanations and inspiring examples, this book is also useful for postgraduate students wishing to conduct qualitative research in the context of an RCT.