A person's concept of self as being male and masculine or female and feminine, or ambivalent, based in part on physical characteristics, parental responses, and psychological and social pressures. It is the internal experience of gender role.

Severe gender dysphoria, coupled with a persistent desire for the physical characteristics and social roles that connote the opposite biological sex. (APA, DSM-IV, 1994)

Mental disorders related to sexual dysfunction, paraphilias, and gender identity disorders.

Persons having a sense of persistent identification with, and expression of, gender-coded behaviors not typically associated with one's anatomical sex at birth, and with or without a desire to undergo SEX REASSIGNMENT PROCEDURES.

Disorder characterized by recurrent, intense sexually arousing fantasies, sexual urges, or behaviors involving cross-dressing in a heterosexual male. The fantasies, urges, or behaviors cause clinically significant distress or impairment in social, occupational or other areas of functioning. (from APA, DSM-IV, 1994)