RTFA: http://www.guardian.co.uk/iran/story/0,,2176958,00…

Iran has between 15,000 and 20,000 transsexuals, according to official statistics, although unofficial estimates put the figure at up to 150,000. Iran carries out more gender change operations than any other country in the world besides Thailand.

Sex changes have been legal since the late Ayatollah Ruhollah Khomeini, spiritual leader of the 1979 Islamic revolution passed a fatwa authorising them nearly 25 years ago. While homosexuality is considered a sin, transsexuality is categorised as an illness subject to cure.