Interest in sexual threesomes is significant, but how much do we really know about them? Why do people engage in them? What influences people’s interest? And what are the longer term ramifications of a threesome? This book explores these questions and more; contextualising the findings in relation to wider norms of gender, sexual behaviour, and relationships. Drawing upon more than 50 interviews and 200+ qualitative surveys this book offers a rich and in-depth analysis of contemporary threesome behaviours. The findings suggest that threesomes are a complex and multi-faceted sexual behaviour. A behaviour which simultaneously resists and maintains norms of monogamy, serves important roles and functions for individuals and relationships, and is both highly desirable but potentially risky. This book would appeal to both undergraduate and postgraduate students as well as postdoctoral scholars in the fields of sociology, psychology, and sexology. In particular, this book is essential reading for those interested in threesomes, consensual non-monogamies, and contemporary norms of sexual behaviour.