Ex-gameshow host Michael Barrymore's entrance into the Big Brother house was seen by an average of 6.5 million people, according to overnight ratings.
Michael Barrymore received a warm welcome from the audience
The launch of Celebrity Big Brother series was seen by one in four UK TV viewers. Last year's series opener was seen by 5.2 million people.
Ratings peaked at 7.6 million viewers - 31.2% of the audience - towards the end of the live broadcast.
Barrymore is the favourite to win the series, at 3/1 with Ladbrokes.
A Channel 4 spokesman said: "We are delighted that last night's launch show has proved such a rating success and a fantastic start to 2006."
Before his entrance last night, Ladbrokes said it had not received a single bet on Barrymore, whose inclusion in the show has caused controversy.
But the presenter - whose TV career has been in ruins since a man was found dead in his swimming pool in 2001 - was given a warm reception by the audience outside the programme's camera-filled house at Borehamwood, Hertfordshire.
Ladbrokes spokesman David Williams said: "We feared he might be damaged goods but the phones started ringing as soon as the show was over.
"The punters have started to make their move for the troubled funnyman."
Barrymore is one of 10 public figures - and one unknown contestant planted by Channel 4 producers - who will spend 23 days in a house with their every move followed by TV cameras.
Other contestants include singer Preston Samuel, of rock band The Ordinary Boys, and rapper Maggot from hip-hop act Goldie Lookin' Chain. Both are rated 4/1 to win.
George Galloway, the first MP to take part in the show, follows at 10/1.
The Respect party leader, who represents the east London constituency of Bethnal Green and Bow, has been criticised for his decision to appear in the programme.
Actress Helen Mirren, who campaigned for his Labour rival Oona King in the 2005 general election, told Radio Five Live: "I think that's very weird. Where does this guy's ambition go, that's very peculiar. Personally, I feel his interest is a self-interest."
George Galloway is the first MP to enter the surveillance gameshow
Other contestants include Faria Alam, who had an affair with England coach Sven-Goran Eriksson, US basketball star Dennis Rodman and model Jodie Marsh.
Actress Rula Lenska, ex-Baywatch star Traci Bingham and 1980s pop star Pete Burns also feature, along with an unknown contestant, Chantelle, who must convince the others she is famous.
Big Brother's ratings success will come under pressure on Friday when it goes head-to-head with ITV1's Soapstar Superstar, a talent show featuring stars from the likes of Coronation Street and Emmerdale in an X Factor-style contest.