Transsexualism is defined as a strong and persistent cross-gender identification with the patient's persistent discomfort with his or her sex and a sense of inappropriateness in the gender role of that sex (Diagnostic and Statistical Manual of Mental Disorders, fourth revision, text revision [DSM-IV-TR]). The disturbance is not concurrent with a physical intersex condition and causes clinical distress or impairment in social, occupational, or other important areas of functioning. The trained mental health professional is obliged to find out if the patient fulfills the criteria of an irreversible gender transposition and if he or she will benefit from medical (hormonal and surgical) sex-reassignment treatment. If a patient has absolved 12 months of real-life experience and at least 6 months of continuous hormonal treatment, the indication for surgical sex reassignment may be given. Genital sex-reassignment in male-to-female transsexuals includes vaginoplasty, preferably by inversion of penoscrotal skin flaps, clitoroplasty, and vulvoplasty. The operation may be performed in one or two sessions. In contrast to genital reassignment in male-to-female patients, no operative standards are available in female-to-male subjects. Recently, neophallus creation from sensate free forearm flaps has emerged as the most promising approach for those patients who want to have a neophallus. Other alternatives such as metoidoioplasty or neophallus reconstruction from regional flaps exist, but are also accompanied by multiple possible complications and re-interventions. Best results are to be expected when using multidisciplinary teams of plastic surgeons, urologists, gynecologists, and experts in sexual medicine in large volume centers. Sohn M, and Bosinski H. Gender identity disorders: Diagnostic and surgical aspects. J Sex Med 2007;4:1193–1208.