On the basis of the records of subjects undergoing cross-gender hormonal treatment at the only gender treatment centre in the Netherlands, the prevalence of transsexualism was assessed over the years 1976–1986. In 1980, the prevalence was 1:45 000 for male-to-female and 1:200 000 for female-to-male transsexuals. In 1986 the prevalence for male-to-female transsexuals was 1:18 000, and for female-to-male transsexuals, 1:54 000. The increased prevalence is apparently due to a lower threshold for applying for medical treatment rather than to a true increase in the prevalence. Nevertheless, the calculated prevalence is higher than hitherto recorded. The ratio of male-to-female compared with female-to-male transsexuals was found to remain constant at 3:1.