This is an evaluation of the therapeutic effect of sex reassignment surgery on 36 female-to-male transsexuals and 105 male-to-female transsexuals in the Netherlands. Data were collected by means of structured interviews. The evaluation was made on the basis of subjective data only, that is on what the persons themselves reported on their gender identity, gender role, and physical condition. Allowing for the restrictive methodology of the (ex post facto) study, it is concluded that there is no reason to doubt the therapeutic effect of sex reassignment surgery. No specific differences were found between those who were still in medical treatment and those who had completed treatment. The findings obtained in the female-to-male transsexuals compare favorably with those obtained in male-to-female transsexuals. Finally, the conclusion is drawn that more attention ought to be paid to psychosocial guidance in addition to medical guidance.