French Open champion and second seed Rafael Nadal made a confident start to his US Open campaign with a straight-sets win over Bobby Reynolds.
The 19-year-old, who has won nine tournaments already this year, broke Reynolds early in the first two sets.
A stunning display of scrambling helped him to the decisive break in game seven of the third, and he closed out the match 6-3 6-3 6-4.
The Spaniard will face Scoville Jenkins of the USA next.
Nadal won his first hard court title at the Montreal Masters earlier this month and hopes to improve on his two previous US Open appearances, when he lost in the second round.
"It's a little bit different," he said. "This year I play very, very well. I played good in Montreal on hard courts.
"Last year when I came here I had lost in Montreal and Cincinnati, first round, so now I have a little bit more confidence."
Earlier, ninth seed Gaston Gaudio became the first big name to fall in the men's draw.
The Argentine, who won the French Open in 2004, lost 7-6 (11-9) 6-2 6-4 to world number 195 Brian Baker of the US.
Baker goes on to face Xavier Malisse, who beat Jan Hernych 6-2 7-5 6-2.
"I was expecting to make a better tournament here, but I played a guy that today was better than me," admitted Gaudio.
Fellow Argentine Guillermo Coria fared better, the eighth seed seeing off experienced Spaniard Felix Mantilla 7-6 6-1 6-3.
France's Richard Gasquet, the 13th seed, looked to have blown a winning position before coming through the fifth set against Alberto Martin for a 6-2 6-3 1-6 6-7 (4-7) 6-4 victory.
Nicolas Massu beat home hope Jan-Michael Gambill 7-6 (7-4) 6-2 6-3, and 18th seed Ivan Ljubicic saw off Tobias Summerer 6-3 7-6 (7-4) 6-3.
Tenth seed Mariano Puerta of Argentina battled past Israel's Noam Okun 7-6 (7-4) 6-7 (3-7) 6-4 6-0, and 24th seed Mikhail Youzhny thrashed Florian Mayer 6-1 6-0 6-2.