SUMMARY
The second half of the twentieth century saw the development within the psychological and medical communities of a transsexual model and procedures for identifying, describing, and treating individuals who sought sex reassignment. This model viewed transsexualism as a form of mental illness characterized by a pervasive and ongoing wish to be a member of the other sex. The model prescribes a set of medical and social procedures called sex reassignment, whereby an individual “changed sex.” The 1990s saw the rise of a new model which explained transsexualism as a natural form of human variability. This model, which continues to gain prominence, views sex reassignment as but one of a variety of acceptable life choices for transsexual individuals, and recognizes the need and right of nontranssexual transgendered people to make similar choices. This paper discusses both models and touches on the social and treatment implications of the rise of the transgender model.