Novak Djokovic began his pursuit of a first French Open title with a straight sets victory over Finland's Jarkko Nieminen.
Djokovic has eight major victories to his name but success at Roland Garros has so far eluded the Serb, who has lost only two matches in 2015.
Nieminen never looked like adding to that tally, despite coming close to taking the second set, as Djokovic sealed a 6-2 7-5 6-2 win in two hours and three minutes.
Two finals in three years are testament to Djokovic's capabilities on clay but it is his irrepressible form this year, combined with Rafael Nadal's indifferent results, that makes the world number one an even greater threat this time around.
Unbeaten now in 23 matches, Djokovic was rarely stretched by Nieminen but when the Finn served for the second set at 5-3, he revealed the sort of fight and persistence that makes him so difficult to beat.
The first set was far more straightforward as Djokovic caught his opponent cold, breaking serve in the opening game and capitalising on a number of unforced errors to go one set clear.
Nieminen, however, loosened up in the second and unleashed a superb backhand pass to break in the fourth game and then serve for the set.
Djokovic flicked into gear, lengthening his groundstrokes and tightening his defence, and Nieminen was unable to cope as the Serb won five games in a row to take the second set and a break immediately in the third.
Nieminen played his part in a handful of entertaining exchanges in the latter stages, but another break of serve allowed Djokovic to move into round two, where he will face either Luxembourg's Gilles Muller or Italian Paolo Lorenzi.
Nadal showed few signs of weakness as he booked his place in the second round with a straight sets win over French wildcard Quentin Halys.
Nadal is bidding to win his 10th title in 11 attempts at Roland Garros but the Spaniard is considered more vulnerable this year, following his worst ever build-up to the tournament.
There was little to concern the nine-time champion on Philippe Chatrier, however, as Nadal claimed a 6-3 6-3 6-4 victory in one hour and 50 minutes.
Dropping to number seven in the world rankings, Nadal is due to face Djokovic in the quarter-finals before a potential last four match-up with Britain's Andy Murray.
It means there will certainly be tougher tests to come than Halys, who is ranked 296th in the world and was playing his first ever match in the main draw of a grand slam.
Nadal, however, will take confidence from an accomplished performance in which the 28-year-old unleashed a number of signature forehands and looked physically at ease throughout.
Two early breaks allowed Nadal to storm into a 4-1 lead and while Halys found his rhythm to take a break back, Nadal broke again to close out the set.
Halys was happy to attempt winners from all over the court and he set up a break point in the third game of the second, but a missed backhand pass saw the opportunity go amiss and it was Nadal who claimed two more breaks to move two sets clear.
The French player gave the home fans several moments to cheer in the latter stages with a number of audacious forehands, but Nadal broke again before sealing a comfortable victory.
Nadal, who will now face fellow Spaniard Nicolas Almagro after he beat Ukraine's Alexandr Dolgopolov in four sets, paid tribute to Halys after the match.
"Quentin is the future, the new style of game he has, trying to hit winners from everywhere - that is the way tennis is moving now," Nadal said.
"Playing at Roland Garros and on centre court for the first time is not easy, so I wish him all the best."
The upset of the day came on court one, where American Jack Sock knocked out 10th seed Grigor Dimitrov in straight sets.
Last year's Wimbledon semi-finalist was beaten 7-6 (9/7) 6-2 6-3, losing in the first round in Paris for the second successive year.
Fourth seed David Ferrer won in straight sets against Slovakia's Lukas Lacko while Richard Gasquet, Marin Cilic and John Isner also went safely through.
