Transsexual subjects are individuals who have a desire to live and be accepted as a member of the opposite sex, usually accompanied by a sense of discomfort with, or inappropriateness of, one's anatomic sex, and a wish to have surgery and hormonal treatment to make one's body as congruent as possible with one's preferred sex. They seek to develop the physical characteristics of the desired gender, and should undergo an effective and safe treatment regimen. The goal of treatment is to rehabilitate the individual as a member of society in the gender he or she identifies with. Sex reassignment procedures necessary for the treatment of transsexual patients are allowed in our country, at Medical Services that have a multidisciplinary team composed of a psychologist, a social worker, a psychiatrist, an endocrinologist and surgeons (gynecologists, plastic surgeons, and urologists). Patients must be between 21 to 75 years old and in psychological and hormonal treatment for at least 2 years. Testosterone is the principal agent used to induce male characteristics in female transsexual patients, and the estrogen is the chosen hormone used to induce the female sexual characteristics in male transsexual patients. Based on our 15 years of experience, we can conclude that testosterone and estradiol treatment in physiological doses are effective and safe in female and male transsexual patients, respectively.