Transsexualism refers to the most extreme form of incongruity between an individual's gender identity and anatomic sex. In 1994, the diagnosis of transsexualism was replaced with ”gender identity disorder" by the DSM-IV committee. Transsexualism is associated with distress because the individual, due to his/her physical characteristics, is not treated as a representative of the gender he/she identifies with and cannot therefore live in a gender role with which he/she identifies. The sexual anatomy of the body also feels alien and inappropriate. Transsexualism that causes distress is treated with sex reassignment therapy. The aim is to alter body characteristics and anatomy closer to those of the target gender as well as to facilitate the integration into the social role of the opposite sex. Investigations and surgery are often only available in specialist centres.