The top seed Novak Djokovic shrugged off his mediocre run-up to the US tennis Open by outclassing Diego Schwartzman of Argentina 6-1 6-2 6-4 to close the first day in New York.
The Wimbledon champion, who won only two matches on the North American hard courts after getting married days after his All England Club triumph last month, sprinted to victory in 97 minutes.
The Serbian world number one will next play Paul-Henri Mathieu of France, who was extended to five sets by Gilles Muller of Luxembourg in a match that included three tie-breaks.
Meanwhile, the French Open champion Maria Sharapova swept the last 10 games to surge past fellow Russian Maria Kirilenko 6-4 6-0 and into the second round of the US Open.
Trailing 2-4 in the first set, the five-times grand slam winner tightened control of her booming groundstrokes to break back, then steamrolled to victory in her return to Flushing Meadows after missing last year's event with a shoulder injury.
Sharapova, the 2006 US champion, will next meet Romania's Alexandra Dulgheru, a straight sets winner over Czech Kristyna Pliskova.
Earlier, the eighth-seeded 2012 champion Andy Murray fought off cramps to beat Dutchman Robin Haase in four painful sets, while women's second seed Simona Halep lost a first-set tiebreak to US debutante Danielle Collins before claiming victory.
And in a fascinating match-up between 19th seed Venus Williams and Kimiko Date-Krumm of Japan, the oldest players in the women's draw, some pesky bees joined in and refused to leave them alone.
Murray looked on his way to an easy victory before he fell victim to cramps that left him stretching and straining to get comfortable before clinching a 6-3 7-6 (6) 1-6 7-5 victory over Haase.
Murray said he might consult with a nutritionist before meeting his second-round opponent, Germany's Matthias Bachinger.
A less serious intrusion bugged the irresistible women's match between seven-times grand slam singles winner Venus Williams and Japan's remarkable Kimiko Date-Krumm, who were beset by bees.
First the 43-year-old Japanese player and later 34-year-old Williams dipped, ducked and danced away before ballgirls helped usher the determined bees off the baseline.
When finally left to play tennis on sun-bathed Arthur Ashe Stadium court, seven-time grand slam singles winner Williams stung Date-Krumm 2-6 6-3 6-3 to advance.
In an upset on the men's side, twice U.S. Open semi-finalist Mikhail Youzhny of Russia, the 21st seed, fell to big-serving Australian teenager Nick Kyrgios 7-5 7-6 2-6 7-6.
The 19-year-old Kyrgios, who made a Wimbledon splash by ousting Rafa Nadal in the fourth round to reach the quarter-finals, blasted in 26 aces.
The 60th-ranked Kyrgios advanced to a second-round match against Italy's Andreas Seppi.
Advancing with relative ease in straight sets were Australian Open champion Stan Wawrinka of Switzerland and fifth-seeded Canadian Milos Raonic.