Three independent reviews of the world literature dealing with the outcome of sex reassignment surgery in transsexualism are presented. In 10-15% of the patients who undergo sex reassignment the results end up in a failure. There are as many failures in the female to male group as in the male to female group. Optimal results from the surgical procedures are important for a successful outcome. Relatively high age when first requesting sex reassignment may be regarded as a risk factor for poor outcome. Genuine transsexuals as a group seem to have a better prognosis for successful outcome of sex reassignment than a group of secondary transsexuals (i.e. transvestites and effeminate homosexuals). On the other hand, secondary transsexuals do better than genuine transsexuals when sex reassignment is refused. It is stressed that great importance should be given to the differential diagnosis when evaluating gender dysphoric patients for sex reassignment.