More than 11.4 million Americans tuned in to watch
take over as host of NBC's The Tonight Show in the wake of
's retirement, the network said on Tuesday.
Twenty percent of households in 56 local markets watching television at midnight (0500 GMT) tuned in to Fallon, it said, sharing preliminary data from Nielsen Media Research.
The figures don't necessarily take into account those who went onto the Internet on Tuesday to catch segments posted on YouTube or on the Hulu streaming website co-owned by NBC.
Eleven million viewers is a strong number by US television standards, particularly in the late-night slot. In prime time, a hit show can expect up to 15 million to 20 million viewers.
NBC said The Tonight Show -- which started a half-hour later than usual due to Winter Olympics coverage -- was "easily the number-one non-Olympic telecast" on Monday, as well as the evening's dominant late-night program across all networks.
Trailing well behind were CBS's The Late Show with David Letterman and ABC's Jimmy Kimmel Live each with five percent of households tuned in.
, 63, signed off from The Tonight Show after 22 years on February 6 as NBC relocated the show from Los Angeles to New York and put Fallon, 39, in the host's chair in a bid to attract a younger, hipper demographic.
"I really don't know how I got here," said Fallon to a cheering studio audience after passing through a blue curtain to take the reins of one of the greatest franchises in American television.
"I just want to do the best I can, and take care of the show for a while," he added. "If you guys let me stick around long enough, maybe I'll get the hang of it."
Fallon's guests Monday included rapper/actor Will Smith and Irish rock band U2, performing atop Rockefeller Center, plus a parade of celebrities including Lady Gaga, Lindsay Lohan, Mike Tyson and Robert De Niro who paid back mock $100 bets that he'd never host the show.
"Welcome to 11:30, bitch!" shouted Stephen Colbert, who hosts his own political late-night show on Comedy Central in the same time slot, as he ceremoniously dumped a bucket of pennies onto the new kid on the block.