The study of human sexual identities is changing, and these changes oblige analysts to think about sexualities in ways never envisioned by their psychoanalytic forebears. These changes also require that they be aware of some of the limitations imposed by their own theoretical traditions. Toward that end, this paper first defines the terms related to modern conceptions of sexuality and sexual identities; then reviews the historical assumptions underlying the theory of bisexuality; and next introduces the role of categories and hierarchies in general and the clinical meaning of sexual hierarchies in particular. After a discussion of the meanings and uses of the “natural,” the paper concludes with a commentary on intersexuality as an example of both the social and the surgical constructions of gender.