Jimmy Fallon’s debut as the host of The Tonight Show was a ratings hit for NBC network.
Viewing-figures firm Nielsen said 11.3 million people watched Jimmy Fallon taking over the show on Monday evening.
But the audience fell short of the 14.6 million viewers who saw Jay Leno sign off as host of the program.
The figures do not necessarily take account of those who watched segments of the show online via services such as YouTube or Hulu.
Jimmy Fallon, 39, will compete against late-night shows hosted by David Letterman on CBS and Jimmy Kimmel on ABC.
Jimmy Kimmel, 46, has proved popular with the key 18-49 demographic.
“I really don’t know how I got here,” Jimmy Fallon, who rose to fame as a cast member on the comedy show Saturday Night Live, told Monday night’s cheering studio audience.
“I just want to do the best I can, and take care of the show for a while. If you guys let me stick around long enough, maybe I’ll get the hang of it.”
Jimmy Fallon’s guests included a parade of celebrities such as Robert De Niro, Will Smith, Lady Gaga and Mike Tyson, plus a performance from the rock band U2.
Jay Leno stepped down for a second time as host of the six-decades-old show on February 6. He originally took over from Johnny Carson in 1992.
Jay Leno briefly retired in 2009, handing over to comedian Conan O’Brien.
But he Leno came back when Conan O’Brien quit amid an attempt by channel executives to reschedule The Tonight Show to later in the evening.
Jimmy Fallon’s debut, coming after the broadcaster’s nightly Olympics program, gained two million more watchers than Conan O’Brien’s debut.
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