Novak Djokovic battled an arm injury, but the world number one and Rafael Nadal were among the winners in the US Open first round.
Defending champion Djokovic needed treatment but got past Pole Jerzy Janowicz on Monday.
Nadal had it far easier against Denis Istomin, while Milos Raonic and Marin Cilic also claimed straight-sets wins.
While Jo-Wilfried Tsonga joined them in advancing, his French countryman Richard Gasquet was the biggest casualty.
DJOKOVIC, NADAL PROGRESS
Despite struggling with a right arm injury, 12-time grand slam champion Djokovic claimed a 6-3 5-7 6-2 6-1 win over Janowicz.
That was the only set dropped by the big names on the opening day at Flushing Meadows.
Nadal crushed Istomin 6-1 6-4 6-2, Raonic was too good for Dustin Brown 7-5 6-3 6-4 and 2014 champion Cilic beat Rogerio Dutra Silva 6-4 7-5 6-1.
The ninth-seeded Tsonga also advanced, too good for Guido Andreozzi 6-3 6-4 6-4.
GASQUET, KLIZAN EXIT
It was a good day for the seeds, with Gasquet (13th seed) and Martin Klizan (28th) the only losers.
Gasquet was thrashed by Brit Kyle Edmund, suffering a 6-2 6-2 6-3 defeat.
Also comprehensively beaten was Klizan, who went down to Russian Mikhail Youzhny 6-2 6-1 6-1.
NADAL CONTINUES RUN, VESELY COMES BACK
Nadal continued his incredible first-round record at the US Open, improving to 12-0 in openers in New York.
Djokovic's next opponent, Jiri Vesely, appeared beaten before rallying from 4-1 down in the fifth set to overcome Saketh Myneni.
There were 11 five-setters on a warm day at Flushing Meadows, including John Isner coming from two-sets-to-love down to beat fellow American Frances Tiafoe.
MONFILS FIGHTS CLOCK
Gael Monfils won his first-round match over Gilles Muller, but he was lucky to avoid injury after an on-court clock he kicked fell.
NADAL SEES IMPROVEMENT, MONFILS GLAD
"My serve worked well almost all the time. I am hitting very well the backhand, but it's true that the forehand I need time. I need confidence and I need to keep practicing the forehand," - Nadal growing in confidence as he continues recovering from a wrist injury.
"I was surprised, because it hurt me a little bit. You know, could be pretty bad. Could have fallen on my ankle or calf and could be more than that," - Monfils glad to avoid injury by clock.
"Definitely one of my best wins in my career. Yeah, very pleasing. Very encouraging the way I played, the way I handled myself, dealt with situations. I thought I was smart with the way I played when I needed to be in certain situations," - Edmund thrilled with his win over Gasquet.
MURRAY BEGINS CAMPAIGN, WAWRINKA FACES VERDASCO
World number two Andy Murray is on Arthur Ashe Stadium during the night session on Tuesday, taking on dangerous Czech Lukas Rosol. Stan Wawrinka meets Fernando Verdasco in a blockbuster first-round clash, while Kei Nishikori, Juan Martin del Potro and Nick Kyrgios are also in action.