Kate Bosworth and Kevin Spacey (second right) head 21's cast
Las Vegas gambling movie 21 has opened at the top of the North American box office chart, with ticket returns worth $23.7m (£11.9m).
The film, starring Kevin Spacey and Kate Bosworth, displaced Dr Suess film Horton Hears A Who! into second place after two weeks at number one.
Spoof action release Superhero Movie was new at number three, with Iraq war drama Stop-Loss new at eight.
UK hit Run, Fat Boy, Run failed to enter inside the top 10.
The comedy, starring Simon Pegg and directed by former Friends star David Schwimmer, was top of the UK and Ireland box office chart last October.
This weekend's US box office takings were 23% down compared to last year, when Blades of Glory was top of the chart.
US BOX OFFICE TOP FIVE
1 21 - $23.7m
2 Horton Hears A Who! - $17.4m
3 Superhero Movie - $9.5m
4 Meet The Browns - $7.8m
5 Drillbit Taylor - $5.8m
Source: Media By Numbers
Media By Numbers, which compiles US box office statistics, said cinema admissions got off to a healthy start in 2008, but are now trailing last year's returns by 2.6%.
But it added 2007 was very strong with blockbusters, including 300, released in the early part of the year.
"Every down weekend has a huge impact on the bottom line," said Media By Numbers president Paul Dergarabedian.