Reigning champion and two-time winner Maria Sharapova and her fellow former world No. 1 Victoria Azarenka were a pair of easy opening-round victors, while Venus Williams bowed out Monday at the French Open.
The second-seeded Sharapova eased past Estonian Kaia Kanepi 6-2, 6-4 on the red clay at Court Chatrier.
A coughing Sharapova was bothered by a cold on Day 2.
"Sharapova's grunt sounds very weird today. Maybe it's the flu?" a tweeter speculated during the match.
"I'm getting over it, and hopefully it will pass by soon," said Sharapova, who titled here in 2012 and last year when she bested Romanian Simona Halep in the final.
The five-time Grand Slam champion Sharapova has reached at least the semifinals the last four years in Paris. In addition to her two titles, the tall Russian was the 2013 Roland Garros runner-up to Serena Williams, who also got the best of Sharapova in January's Aussie finale.
Sharapova's second-round opponent will be fellow Russian Vitalia Diatchenko.
The two-time Aussie Open champion and two-time U.S. Open runner-up Azarenka, seeded 27th at this French fortnight, routed Spaniard Maria-Teresa Torro-Flor 6-2, 6-1. Azarenka missed last year's French Open due to a foot injury.
A 15th-seeded Venus was vanquished by fellow American Sloane Stephens, 7-6 (7-5), 6-1.
The seven-time Grand Slam winner Venus was a French Open runner-up to her younger sister Serena in 2002 and hasn't reached a quarterfinal in Paris since 2006.
Suarez Navarro, who was the runner-up to Sharapova in Rome two weeks ago, advanced with a 6-2, 6-2 win over Romanian Monica Niculescu. A two-time French Open quarterfinalist, Suarez Navarro won her WTA-leading 32nd match of the year.
Kerber, who already owns two clay-court titles this season, routed Hungarian Timea Babos 6-0, 6-1.
An upset came when German Annika Beck doused 14th-seeded former Wimbledon runner-up Agnieszka Radwanska 6-2, 3-6, 6-1 at Stade Roland Garros.
In other action involving seeds, No. 17 former French Open runner-up Sara Errani of Italy held off American Alison Riske 7-6 (7-1), 2-6, 6-0; No. 19 Ukrainian Elina Svitolina blitzed Belgian Yanina Wickmayer 6-2, 6-2; No. 20 former Wimbledon runner-up Sabine Lisicki of Germany mauled Puerto Rican Monica Puig 6-3, 6-2; Bulgarian Tsvetana Pironkova doused No. 27 Czech Barbora Strycova 7-6 (7-5), 6-2; No. 26 Aussie Samantha Stosur drilled American Madison Brengle 6-1, 6-3; No. 29 French favorite Alize Cornet overcame Italian Roberta Vinci, a runner-up in Nurnberg last week, 4-6, 6-4, 6-1; and Mo. 30 Romanian Irina-Camelia Begu dismissed American Bethanie Mattek-Sands 6-4, 7-6 (8-6). The former U.S. Open champion Stosur is fresh off her clay-court title in Strasbourg, France.
Several other women reached the second round, including Romanian Alexandra Dulgheru, Czech Lucie Hradecka, Brit Heather Watson and France's Virginie Razzano.
On Tuesday, the world No. 1 superstar Serena will open her stay against Czech Andrea Hlavackova.
Serena owns 19 majors singles titles, including French Open ones in 2002 and 2013. The powerful American is the reigning Aussie and U.S. Open champ and has lost only one match in 2015 (25-1).
Also taking to the courts for first-round matches on Tuesday will be fourth- seeded Wimbledon titlist Petra Kvitova, fifth-seeded former No. 1 and 2014 U.S. Open runner-up Caroline Wozniacki, sixth-seeded Wimbledon runner-up Genie Bouchard and 16th-seeded rising American star Madison Keys, who reached the Aussie Open semis back in January.