Five-time champion Roger Federer powered through his opening match against Santiago Giraldo at the US Open despite a surprising wobble early on.
The Swiss, 30, let a double-break lead slip from 5-1 but then showed flashes of his brilliant best as he defeated the Colombian 6-4 6-3 6-2.
Leading American Mardy Fish began his US Open campaign by demolishing Germany's Tobias Kamke 6-2 6-2 6-1.
Seventh seed Gael Monfils and ninth seed Tomas Berdych also progressed.
Czech star Berdych enjoyed an easy win, thumping French qualifier Romain Jouan 6-2 7-6 (7-4) 6-1 to reach round two, and Monfils, a quarter-finalist at Flushing Meadows last year, began his campaign with a 7-6 (7-4) 6-3 6-4 win over Grigor Dimitrov.
Federer will end the year without a Grand Slam title for the first time since 2002 if he fails to win in New York, and amid the characteristic shot-making ability there were also the lapses in form against Giraldo that have afflicted him recently.
"As the match went on, I think I started to get more solid and better, and that's a good feeling to have," said Federer, who equalled Andre Agassi's tally of 224 Grand Slam match wins in the Open Era, second only to Jimmy Connors' 233.
"I don't care how I do it. It doesn't need to be pretty. I don't think I've ever played my very, very best in the first round."
The world number three played a woeful service game to allow Giraldo back to 5-4 from 5-1 down, only for the Swiss to move through the gears and take the set in the next game.
Federer looked in great shape at 3-0 up in the second set before again letting his opponent back in with a break of serve, but the world number 54 did not have enough in his game to capitalise.
There were no serious alarms for the Swiss star but he will need to improve on a final tally of 35 unforced errors in the tougher tests to come, with Israel's Dudi Sela waiting in round two.
Afterwards, Federer admitted he struggled to adjust to the slow pace of the Flushing Meadows courts this year.
"It's just unfortunate maybe that all the slams are too equal," he said. "This should feel very different to the Australian Open and it doesn't. I don't think it's really what tennis needs."
Fish, 29, has overtaken Andy Roddick as the highest-ranked American during a remarkable rise over the last 12 months and is the only man from the United States in the world's top 10.
He opened the first day's play on Arthur Ashe Stadium and took just one hour and 43 minutes to secure his progress against Kamke, hitting 28 winners in 23 games.
"It's an honour to be able to start the tournament off on that court," he said. "It's just an amazing court.
"It's probably pretty easy to say this is one of the biggest tournaments I've ever played, coming in where I've come into it. I've never come into a Grand Slam ranked higher."
French 13th seed Richard Gasquet was another convincing winner, hammering Ukrainian Sergiy Stakhovsky 6-4 6-4 6-0.
Among the other seeds to progress in straight sets were Serbian Janko Tipsarevic, who overcame France's Augustin Gensse 6-2 7-5 6-0 and Radek Stepanek of the Czech Republic, who beat Germany's Philipp Kohlschreiber 6-4 6-1 6-3.
Fifteenth seed Viktor Troicki became the first seed to exit the tournament when he was beaten 3-6 6-3 4-6 7-5 7-5 by Alejandro Falla of Colombia.