Sweden was the first country to legislate on sex reassignment procedures in 1972. Patients with gender dysphoria are in Sweden referred to one of six university clinics specialised in the field; all surgery, however, is centralised to the Karolinska Hospital in Stockholm. The aetiological strivings regarding transsexualism have to date been inconclusive; however, several lines of evidence speak in favour of an early biological influence on gender identity. The vast majority of studies addressing outcome have provided convincing evidence for the benefit of sex reassignment surgery in carefully selected cases. The current article summarises the state of the art regarding work-up and treatment of transsexuals.