This chapter provides an overview of qualitative research methods in health technology assessment (HTA). It discusses the scope of the review, the historical context of qualitative methods, and the relationship between qualitative and quantitative approaches. The chapter highlights the importance of understanding the principles and applications of qualitative methods for commissioners and researchers. It emphasizes that qualitative research is useful in exploratory stages, conceptualization, and generating hypotheses, as well as in interpreting and qualifying quantitative findings. The chapter also covers sampling, generalization, and ethical considerations in qualitative research. It concludes by discussing the strengths and limitations of qualitative approaches and their potential value in HTA.This chapter provides an overview of qualitative research methods in health technology assessment (HTA). It discusses the scope of the review, the historical context of qualitative methods, and the relationship between qualitative and quantitative approaches. The chapter highlights the importance of understanding the principles and applications of qualitative methods for commissioners and researchers. It emphasizes that qualitative research is useful in exploratory stages, conceptualization, and generating hypotheses, as well as in interpreting and qualifying quantitative findings. The chapter also covers sampling, generalization, and ethical considerations in qualitative research. It concludes by discussing the strengths and limitations of qualitative approaches and their potential value in HTA.