Robbie Williams has checked into a rehab centre in the US.
The singer, who has sold 50 million albums worldwide, is said to be seeking help for an addiction to prescription drugs.
Williams, 33 today, is currently on a break after cancelling tour dates because of exhaustion.
In a statement, his publicity agency said: "Robbie Williams has today been admitted into a treatment centre in America for his dependency on prescription drugs.
"There will be no further comment on this matter."
The news follows a difficult few months for Williams, who has had problems in the past with drink and drugs.
His new album Rudebox has failed to live up to the success of his previous offerings and he missed out on nominations for the top Brit Awards.
Williams has also seen his former band-mates, Take That, reform and launch a successful comeback.
Gary Barlow, Jason Orange, Mark Owen and Howard Donald had a number one hit with Patience and their album, Beautiful World, went multi-platinum.