In the first section of the book, Bailey discusses gender-atypical behavior and gender dysphoria in children, emphasizing the biological determination of gender. In the second section, he deals primarily with gay men, including the link between childhood gender dysphoria and male homosexuality later in life. Bailey reviews evidence that male homosexuality is congenital (a result of genetics and prenatal environment), and he argues for the accuracy of some stereotypes about gay men. In the third section, Bailey summarizes evidence for a psychological typology of trans women that says there are two forms of transsexualism that affect transgender women: one that he describes as an extreme type of male homosexuality and one that is a sexual interest in having a female body, called autogynephilia.