The prevalence of transsexualism in the Netherlands was estimated by counting all the subjects who were diagnosed as transsexuals by psychiatrists or psychologists and were subsequently hormonally treated and generally underwent sex-reassignment surgery. At the end of 1990, 713 Dutch-born transsexuals received treatment (507 men, 206 women). This amounts to a prevalence of 1:11,900 for male-to-female transsexualism and 1:30,400 for female-to-male transsexualism (population age 15 and above in both groups). The sex ratio was about 2.5 men to 1 woman. The most important reason for this relatively high prevalence seems to be the benevolent climate for the treatment of transsexualism in the Netherlands.