Serena Williams advanced to the second round of the French Open by beating Kristie Ahn 7-6 (2), 6-0.
The sixth-seeded Williams served for the match at 40-0 but Ahn saved three match points. An ace gave her a fourth opportunity to win but she hit a shot into the net.
Williams then saved a break point before finally beating her American opponent with an ace.
Ahn held leads of 3-1 and 4-2 in the first set.
The 39-year-old Williams is a three-time French Open champion and is looking to equal Margaret Court's record of 24 major titles. She will next face Bulgarian wild-card entry Tsvetana Pironkova.
Last year's runner-up Marketa Vondrousova lost in the first round of the French Open.
The 15th-seeded Czech player was beaten by Iga Swiatek 6-1, 6-2.
Vondrousova was the third-lowest ranked player to reach the final last year when she did so at No. 38.
Swiatek reached the fourth round at Roland Garros last year. The 19-year-old Polish player will next face Hsieh Su-wei of Taiwan.
Petra Kvitova reached to the second round of the French Open after a 6-3, 7-5 win over Oceane Dodin under the new roof on Court Philippe Chatrier.
The two-time Wimbledon champion advanced from the first round for the 10th time in 11 appearances at Roland Garros. The Czech player's only first-round loss was in 2010. She was a semifinalist in 2012. She is ranked 11th and seeded seventh at Roland Garros.
A forehand hit wide by 118th-ranked Dodin gave Kvitova a break of serve in the second set. The 23-year-old Frenchwoman was playing the 30-year-old Kvitova for the first time.