What do the psychologists say?

“Transvestism is a fetishistic preoccupation partly with the female wardrobe and partly with the woman as such”
Danish psychologist Preben Hertoft, Psychosexual Problems, 1976

Most cross-dressers are heterosexuals with an otherwise normal sex-life. It just so happens that wearing female clothes turns them on – either as a prelude to masturbation or in some cases simply as a means of achieving a feeling of psychological release. Often their wives or girlfriends are unaware of their transvestism.
Alan Isaacs, Sex and Sexuality: A Thematic Dictionary of Quotations, Cassell, 1993