Brad Pitt and George Clooney have returned to the stage to perform at the Los Angeles premiere of 8.

The Hollywood stars played United States District Chief Judge Vaughn R Walker and a lawyer respectively in the star-studded cast of Dustin Lance Black's play, which is about the 2010 court fight against the gay-marriage ban, Proposition 8, that California voters approved in 2008.

Martin Sheen received a standing ovation for his portrayal of an attorney arguing for gay-marriage rights, while Jane Lynch played a homophobe against same-sex marriage, reported Access Hollywood.

Kevin Bacon, Jamie Lee Curtis, George Takei, John C Reilly, Christina Lahti, and Glee stars Matthew Morrison and Chris Colfer also had roles in the play, which premiered at the Wilshire Ebell Theatre.

The benefit performance, which was directed by Rob Reiner, was broadcast live on YouTube.

John C Reilly - who was originally meant to play Brad's role - revealed he was moved by the material, and even more so by its message.

"I think America will be a better place and we can hold our chins up a little higher in this country when everyone is treated (equally)," he said.

"These aren't gay rights or special rights, they're basic rights that people who love each other should have," he added.

Source: Press Release