The authorities allowed only one screening of the 40-minute exploration of Iranian attitudes to sex-change operations before an invited audience of 100 people in Tehran's Artists' House.
That it was shown at all was largely thanks to a little-known religious edict by Ayatollah Khomeini, the late revolutionary leader, who ruled that such operations were an acceptable last resort for patients whose self-image was irreconcilably at odds with their birth sex.
Sharareh Attari, 32, directed the documentary, It Happens Sometimes, and said she was not surprised that it had been denied a wider release.
It showed that "society moves slowly" in accepting difference, she said.
Khosro Sinayee, 65, an experienced director who was among the audience at the premiere, praised the young film-maker's "courage and determination" in tackling the issue.
"The jury is still out as to whether there has been a real shift in what is acceptable in Iran but it's in the nature of young people to push the boundaries"
"The jury is still out as to whether there has been a real shift in what is acceptable in Iran but it's in the nature of young people to push the boundaries," he said.
"[Iran's young] were born into this system and they laugh at the threat of harsh treatment that held so much fear for my generation.
"They just don't see the boundaries as being in the same places."
An 'irreconcilable conflict'
The documentary tells the story of Amir, a 21-year-old who feels like a woman trapped in a man's body and undergoes a sex operation to become Rima.
"Nothing has changed except my sex," Rima says after the surgery.
Rima asks an Islamic scholar for
guidance on her situation
But, as the movie's opening sequences reveal, few of Rima's fellow Iranians see things that way.
A Muslim cleric interviewed on a bus insists that "transsexuals have no respect for God and therefore can have none for themselves".
A mother says simply: "They're not like us."
It is left to surgeon Barham Mirjalali to say that sometimes people are born with an irreconcilable conflict between their birth sex and their self-image.
Ali, a transvestite friend of Amir who prefers to be called Hilda, says that he changes his clothes and puts on his make-up in a car park because of the incomprehension and disapproval of his family.
The father of another friend offers to pay for his son's sex -change operation on one condition - that the family never see or hear from him again.
Amir's own mother, Nasrin, says that as a nurse she has "often heard of such things" but "cannot get used to the situation", as she has no idea what to tell the neighbours.
After the operation, even Rima has doubts about what she has done, so she travels to Iran's Shia clerical capital of Qom to seek reassurance.
There, a theologian tells her that "changing sex is not the same as changing soul" and that even Ayatollah Khomeini sanctioned such operations as a last resort.
However, such happy endings remain a rarity in the Islamic republic, the surgeon featured in the documentary says after the screening.
Mirjalali said he had "large numbers of patients who have only just begun to accept their fate or overcome the misgivings of those around them".
Among those who felt unable to go ahead with a sex change, because of the opposition of their friends or family, he said he had recorded "numerous suicide attempts".