Treatment outcome in transsexuals is expected to be more favourable when puberty is suppressed than when treatment is started after Tanner stage 4 or 5. In the Dutch protocol for the treatment of transsexual adolescents, candidates are considered eligible for the suppression of endogenous puberty when they fulfil the Diagnostic and Statistic Manual of Mental Disorders-IV-RT criteria for gender disorder, have suffered from lifelong extreme gender dysphoria, are psychologically stable and live in a supportive environment. Suppression of puberty should be considered as supporting the diagnostic procedure, but not as the ultimate treatment. If the patient, after extensive exploring of his/her sex reassignment (SR) wish, no longer pursues SR, pubertal suppression can be discontinued. Otherwise, cross-sex hormone treatment can be given at 16 years, if there are no contraindications. Treatment consists of a GnRH analogue (GnRHa) to suppress endogenous gonadal stimulation from B2-3 and G3-4, and prevents development of irreversible sex characteristics of the unwanted sex. From the age of 16 years, cross-sex steroid hormones are added to the GnRHa medication. Preliminary findings suggest that a decrease in height velocity and bone maturation occurs. Body proportions, as measured by sitting height and sitting-height/height ratio, remains in the normal range. Total bone density remains in the same range during the years of puberty suppression, whereas it significantly increases on cross-sex steroid hormone treatment. GnRHa treatment appears to be an important contribution to the clinical management of gender identity disorder in transsexual adolescents.