Mortality in male-to-female and female-to-male transsexuals is not increased during cross-sex hormone treatment. Transdermal oestradiol administration is recommended in male-to-female transsexuals, particularly in the population over 40 years in whom a high incidence of venous thromboembolism was observed with oral oestrogens. It seems that in view of the deep psychological needs of transsexuals to undergo sex reassignment, our treatment schedule of cross-sex hormone administration is acceptably safe.