Rikshospitalet (The National Hospital) treats all transsexual patients in Norway. 50-70 patients are referred annually for assessment and about 20 of these are diagnosed as transsexual. Approximately 15 confirmed transsexuals, who have received hormone treatment, are referred to sex reassignment surgery per year. This article describes diagnosis and treatment of transsexualism with an emphasis on surgery.The article is based on a non-systematic review of the literature and our own clinical experience.Patients are evaluated for sex reassignment surgery after at least one year of psychiatric evaluation and an additional year of endocrine treatment. Male-to-female patients are evaluated for breast augmentation if hormone therapy has given unsatisfactory results. Thereafter, genital surgery can be performed, i.e. the testis and corpus cavernosum are removed and a neovagina and neoclitoris are constructed. Female-to-male patients have the possibility to undergo breast reduction, hysterectomy, salpingoophorectomy and construction of a neopenis. If the patient responds well to male hormones, the clitoris can be straightened and reconstructed as a small neopenis with an erectile function (metaidoioplasty). Alternatively, phalloplasty is performed using the local groin flap or a microvascular free flap.Sex reassignment surgery mainly consists of operations on breasts and genitalia.