surgery to change, within the limits of surgical possibility, a person's genitals to those of the other sex (and retain the possibility of sexual stimulation). In male-to-female conversion, the penis is converted to a vagina. In female-to-male conversion, the challenge has been to create a version of a penis.

Sex reassignment surgery (SRS) is a term for the surgical procedures by which a person's physical appearance and function of their existing sexual characteristics are changed to that of the other sex. It is part of a treatment for gender identity disorder in transsexual and transgender people. It may also be performed on intersex people, often in infancy.