Almost two million people are expected at a free Rolling Stones gig in Rio de Janeiro, a city official has said.
The stage for the concert is still being erected
"This is the biggest live show that has ever occurred in the world," said the city's health secretary, Flavio Tanure.
But Saturday's crowd may not be as big as that at Rod Stewart's 1994 concert, also at Copacabana beach, which drew a crowd of 3.5 million.
About 10,000 police officers will be on duty for the show which is part of the Stones' Bigger Bang world tour.
The huge stage will be surrounded by eight video screens and 16 sound towers.
The city is paying $750,000 (£432,000) for the gig, which takes place just a week before Rio's famous carnival.
Fans are snapping up merchandise before the gig
Fans in the US will be able to listen to the show on radio and on the internet and also in more than 150 cinema screens across the country.
There have been some concerns about security after three people were crushed to death in Sao Paulo earlier this month at an autograph session by Mexican band RBD.
But Brazilian authorities said it was all in hand.
"It's similar to New Year, and we have significant experience with live shows on the beach," said Mr Tanure.
Rio de Janeiro's annual New Year party attracts huge crowds with various bands and fireworks.
It is the third time the Rolling Stones have performed in Brazil but the first time they have played for free - the mayor, Cesar Maia, said tourists from as far away as Chile were coming for the concert.