[Diagnosing gender identity].

Transsexualism and other variations of gender identity are based on a stable sense of identity. The aetiology of this phenomenon is not fully known. Suffering caused by gender dysphoria is alleviated with sex reassignment. The psychiatric assessment of both adolescents and adults has been centralized in Finland to two university hospitals, the Helsinki University Hospital and Tampere University Hospital. In both hospitals, multidisciplinary teams aim at differential diagnosis by using well-known psychiatric and psychological instruments. Wishes for sex reassignment that are caused by a mental health disorder are excluded. Assessment in adolescence is challenging because the identity in youth is still forming.