Defending French Open champion Maria Sharapova came through her first round match at Rolland Garros unscathed after she beat Spain's Kaia Kanepi 6-2 6-4.
Sharapova appeared unwell during her victory on Philippe Chatrier as she coughed and spluttered between points, but the Russian insists it is not a major concern.
"It's just the way it is. I'm getting over it and hopefully it will pass by soon," Sharapova said.
"It was really the least of my worries today. It's such a big occasion obviously for me to be out, back on centre court, and I had a tough opponent ahead of me.
"I wanted to win the match but I knew it was going to be tough and it wasn't going to depend on the tennis.
"The conditions were pretty difficult as well, so overall I'm just happy I got through and to have a day off tomorrow and I should be better by then."
Nine-time grand slam champion Venus Williams is out after she lost 7-6 (7/5) 6-1 in the all-American clash with Sloane Stephens.
Williams, who was seeded 15th in the draw, made more than twice as many unforced errors as her 22-year-old opponent, who will now play Britain's Heather Watson in round two.
Watson overcame French wildcard Mathilde Johansson 6-4 7-5 but she will be the only Briton in the second round of the women's draw after Johanna Konta lost 7-6 (19/17) 4-6 6-2 to Czech Denisa Allertova.
Eighth seed Carla Suarez Navarro is also into the next round after she beat Romania's Monica Niculescu in straight sets.
Former world number two Agnieszka Radwanska crashed out as she lost 6-2 3-6 6-1 to Germany's Annika Beck.
Radwanska, who was seeded 14th at Roland Garros, has dropped out of the top 10 this year after a poor run of results and her struggles continued against Beck, who is ranked 81st in the world.
The pair's previous meeting had resulted in a 6-0 6-0 win for Radwanska but the Pole was unable to repeat the feat, and it is Beck who goes through to the second round.
"That was two years ago and different conditions so we shouldn't really compare," Radwanska said.
"It was a really strange match. I started pretty slow and it was too late in that first set.
"I was much better in the second set. I thought I was still playing my game in the third set, but it just went too fast the other way.
"The clay season is not really my favourite one, and I guess it's not getting better, even when I'm really trying to do everything.
"I just want to forget about that and focus on grass now."
Third seed Simona Halep came through unscathed as she beat Russia's Evgeniya Rodina 7-5 6-4.
Halep, who is yet to win a grand slam, lost in the deciding set of last year's final to Maria Sharapova and is considered a serious contender again for the title in Roland Garros.
She was never at her fluent best against Rodina, in what was the opening match of the tournament on Philippe Chatrier, but her potent ground strokes proved too much for her opponent, who is ranked 91st in the world.
"It was a tough match because it was the first round and it's always difficult to start the tournament," said Halep, who now faces Croatia's Mirjana Lucic-Baroni in round two.
"She played well and I did make easy mistakes, but it's normal and I accept that. Next round I will be better, for sure."
Halep faces a potential reunion with Sharapova in the semi-finals but the world number three insists she is a better player than the one that lost to the Russian last year.
"I'm stronger than last year, I think mentally, and I'm stronger as well on court," Halep said.
"My serve is better so I feel more confident now with my game but, still, it's about the match and about the opponent, so I have to train hard and be focused in every game."
Croatian teenager Donna Vekic claimed the first scalp of the round as she knocked out France's 31st seed Caroline Garcia with a 3-6 6-3 6-2 victory.
The 18-year-old, who has previously worked under Tim Henman's former coach David Felgate, admitted it took her time to settle on Philippe Chatrier.
"It was my first time in such a big stadium," said Vekic, who plays Serbia's Bojana Jovanovski in the second round.
"She was French and favourite and the crowd was supporting her.
"I warmed up on the court and I was like, 'I'm okay' but then I went out in the knock-up and was like, 'Oh, my God.'
"There were so many people. I was so nervous in the first set. I finally loosened up and then started playing better."
Russia's ninth seed Ekaterina Makarova is also through after she overcame American Louisa Chirico 6-4 6-2, while last year's conqueror of Serena Williams, Garbine Muguruza, beat Croatia's Petra Martic 6-2 7-5.
Muguruza is seeded 21st in this year's draw and will now face Italian Camila Giorgi.
"I was really, really nervous," Muguruza said.
"The first match of the next year when you had a good tournament last year you feel a lot of pressure.
"So I'm just happy to win the match. Sometimes when you are too nervous you block yourself and you cannot play. I'm happy this did not happen."
Seventh seed Ana Ivanovic had to come from a set down to beat Kazakhstan's Yaroslava Shvedova 4-6 6-2 6-0 while 28th seed Flavia Pennetta was also taken to a decider by Poland's Magda Linette before coming through 6-3 5-7 6-1.
