This is an overview of the rise of sexological theories about female homosexuality. The field consistently made connections between homosexuality and neurosis in women, as well as connecting the former with “inversion” or masculinity. Different part of the field gave different weight to ideas of genetic versus behavioral causes. There were also systematic ways in which the sexological approach to homosexuality differed for men and women. But the overall concept pressured women with homoerotic feelings to consider themselves mentally—and perhaps physically—ill.