What is the nature of sexual orientation and how does it develop? Ideas about erotic attraction have evolved with our society, reflecting changing concepts of masculinity, femininity, morality, and individual identity. Though the line between homosexuality and heterosexuality used to be sharply drawn, Kinsey's original research threw this practice into question, suggesting these labels stand as two poles on a continuum of human behavior. In this second volume of the Kinsey Institute Series, editors David P. McWhirter, June Machover Reinisch, and Stephanie A. Sanders have collected the work of distinguished researchers and clinicians in many fields who seek to understand what we have learned about the factors influencing sexual orientation, and what approaches and research tools are most appropriate in its investigation. Drawing on their experience and expertise, these contributors provide answers from many viewpoints--historical, biological, developmental, cultural, psychoanalytic, and even primate behavior. In particular, they examine what shapes and changes sexual orientation across cultures, lifespan, and species. This volume reflects research being done on many fronts to extend Kinsey's formulation of sexuality and investigate it more fully. Providing a critical presentation of traditional views as well as recent theory, Homosexuality/Heterosexuality is written for a readership of professionals and lay people, and will be useful as both a reliable fund of information and a source of innovative ideas on the study of human sexual behavior.