The International Handbook on the Demography of Sexuality is the first book to specifically address the study of sexuality from a demographic perspective. Demographic research has largely paid little attention to sexuality as a whole, or sexual orientation in particular, other than in studies examining the “consequences” of sex – sexually transmitted infections or fertility. Instead, the content of this handbook explores population sexuality in order to describe the prevalence of sexual behaviors, desires, and identities, as well as their connections with other demographic outcomes. The focus is on analyzing sexuality as a demographic topic in its own right, rather than solely as a variable in studies of sexually transmitted infection or other health-related topics. In this book, both researchers with traditional demographic backgrounds, as well as those with training in other disciplines, provide an overview of the state of current research on population sexuality. These chapters provide a foundation for the development of research in the burgeoning field of the demography of sexuality.