From the Independent:

Transsexuals are permitted to have sex-change operations in Iran by the decree of Ayatollah Ruhollah Khomeini himself. The founder of the Islamic republic passed a fatwa allowing one transsexual woman to have the operation because sexual ambiguity made it impossible for her to carry out her religious duties properly. Iran now has dozens of people who have had a sex change.

Full Story: The Independent: Ten very surprising things about Iran