Gender Identity Disorder (GID) is a mental health diagnosis that is currently treated through a triadic medical model which involves hormone therapy, the real life experience, and various forms of surgery, including genital surgery. The aim of treatment is to ameliorate the dysphoria and anxiety symptoms associated with being gender incongruent. Surgical options have grown and improved over the last four decades and most of the research conducted in the area is associated with transsexuals who seek this treatment option. The findings of previous research have generally shown high satisfaction with surgical outcomes. However, limitations of the current treatment model are identifiable. Notably, due to the invasive and irreversible nature of surgery, the guidelines for inclusion in surgical procedures are stringent and exclude many transsexuals. Many studies have focussed on identifying risk and protective factors that predict good surgical outcomes. However, this process has not reflected the mental health outcomes of many transsexuals who do not seek the triadic medical model of treatment. Additionally, there has been a lack of theoretical application from a psychological perspective to guide treatment protocols. The present project used a theoretical framework based on the two core components of this disorder, gender and identity, by utilising identity theory and self-discrepancy theory to help explain the interplay between being gender incongruent and achieving gender congruence post transition. The project was the first study of its genre conducted with an Australian and New Zealand sample. The project utilised a subjective definition of transition which is different to the objective definition of transition defined by the medical model as engaging in hormone therapy, living as the preferred gender and the completion of sex reassignment surgery (SRS).