Venus Williams bounced back from a poor start at the French Open on Sunday, beating 19-year-old Paula Ormaechea 4-6, 6-1, 6-3 in her first Grand Slam match since revealing she has been diagnosed with an autoimmune disease.
The seven-time major champion seemed taken aback by her opponent's early aggressive play, but still managed to turn the match her way and reach the second round.
The 31-year-old Williams, a former top-ranked player who is now No. 53, is 12-4 this season.
Williams pulled out of the U.S. Open last August before her second-round match, saying she had Sjogren's syndrome, an autoimmune disease that can cause fatigue and joint pain. She returned to the tour in March.
Williams, seven-times a Grand Slam title winner and runner-up here to sister Serena in 2002, faces either Polish third seed Agnieszka Radwanska or Bojana Jovanovski of Serbia for a place in the third round.
Russia's Svetlana Kuznetsova marked her 40th Grand Slam appearance with a comfortable 6-1, 6-3 win over Croatian world number 117 Mirjana Lucic.
The Russian who won the French Open title in 2009 is seeded No. 26 this year faced little trouble despite being broken twice in the second set.
The 30-year-old Lucic reached the Wimbledon semi-finals in 1999, but she is now 11-44 against players ranked in the top 30 in her career.
Kuznetsova, also the 2004 US Open champion, next tackles either Kateryna Bondarenko of Ukraine or Taiwan qualifier Chan Yung-Jan.
"I love this tournament. Even before I won I always enjoyed coming here," Kuznetsova said. "It's (a) special atmosphere here."
No. 20 Lucie Safarova of the Czech Republic also advanced, beating Anastasiya Yakimova of Belarus 6-2, 6-0. American players Melanie Oudin and Irina Falconi also reached the second round.
German 10th seed Angelique Kerber proved too strong for her Chinese opponent Shuai Zhang 6-3 6-4.
Meanwhile, 2008 French champion Ana Ivanovic blew kisses to the crowd after making short work of Spanish qualifier Lara Arruabarrena-Vecino in her opening match.
The Serbian, seeded 13th, finished off a 59-minute 6-1 6-1 demolition with an ace.
Former world number one Ana Ivanovic admitted after the game that getting back to the top ranking of women's tennis is tougher than the first time around but she's enjoying competition again after a period of self-doubt.
"I think it's harder getting back than actually getting there in the first place," the Serbian number 14 said after beating Spain's number 135 Arruabarrena-Vecino.
Ivanovic, who is making her eighth consecutive appearance at the French Open, added: "I feel like myself again, you know, and I'm enjoying competition. I'm just enjoying to be out there and to challenge top players and to be challenged as well. I think that's what it's all about".
Ivanovic will face Israel's Shahar Peer for a place in the last 32.