A benefit concert for the victims of the Haiti earthquake, hosted by George Clooney and featuring Jay-Z and Madonna, is taking place in New York, Los Angeles, London and Haiti.
Other acts taking part in the two-hour Hope for Haiti telethon include Bono, The Edge and Rihanna, who pre-recorded their performances in London on Friday.
The concert is being shown on all major US TV channels, MTV in the UK, and worldwide on YouTube with more than 100 Hollywood and music stars set to take part.
Haitian-born rapper Wyclef Jean - who set up the charity foundation Yele Haiti - Bruce Springsteen, Jennifer Hudson, Mary J Blige, Shakira and Sting are performing in New York.
Rihanna, meanwhile, is performing a cover version of Bob Marley's Redemption Song, which she has released to raise money for the people of Haiti.
Film stars making appearances include Brad Pitt, Ben Stiller, Clint Eastwood, Denzel Washington, Halle Berry, Julia Roberts, Leonardo DiCaprio, Matt Damon, Meryl Streep, Nicole Kidman, Tom Hanks and Will Smith.
George Clooney, who organised the event, told MTV: "It's a big world out there, and we all have a lot of responsibility to look out for people who can't look out for themselves."
"So what we can do is first and foremost, raise money. Period. That's it ...
"If I thought we could all pick up shovels and go in there and help without being in the way, I think a lot of people would do that."
Clooney will be donating $1m during the telethon, his spokesman told Reuters news agency.
Other stars have also been giving to the victims of the quake.
Actor Leonardo DiCaprio signed a cheque for $1m to the Clinton Bush Haiti Fund, which was started by former Presidents Bill Clinton and George W Bush.
Meanwhile, Rod Stewart, Leona Lewis, JLS and Michael Buble have signed up to provide vocals for a Haiti charity single, organised by Simon Cowell.
They will record a cover of REM's ballad Everybody Hurts.