Autogynephilia (sexual arousal in men produced by the thought or image of themselves as women) is often associated with gender dysphoria (the desire to belong to the opposite sex). Previous research has shown that autogynephiles who are principally aroused by images of themselves as nude women are more gender dysphoric than those principally aroused by images of themselves as partially or fully dressed women. This study tested the hypothesis that the feature of the nude self-image most responsible for its correlation with gender dysphoria is the imagined vulva. The subjects were 220 nonhomosexual male outpatients who reported sexual arousal while imagining themselves with one or more features of the female anatomy. Autogynephilia and gender dysphoria were assessed with questionnaires. The findings confirmed that men who are sexually aroused at the thought of having a vulva are more likely to want to be women.