Justine Henin-Hardenne returned from a three-month lay-off to beat Barbora Strycova in the first round of the Olympic women's tennis singles event.
The Belgian world number one, who had not played for 11 weeks because of a virus, overcame the Czech 6-3 6-4.
Reigning champion Venus Williams began her title defence by beating Melinda Czink of Hungary 6-1 6-2.
And Martina Navratilova enjoyed her Olympic debut at the age of 47 with victory in the women's doubles.
The American teamed up with Lisa Raymond to beat Ukrainian pair Yuliya
Beygelzimer and Tatyana Perebiynis 6-0 6-2.
Navratilova received a standing ovation at the beginning and end of the match.
Two months short of her 48th birthday, Navratilova became the oldest tennis player to appear at an Olympics.
American tennis player Blanche Hilliard was 44 at the 1908 London Olympics and Norman Brookes of Australia was 46 when he competed at the 1924
Meanwhile, Spain's Arantxa Sanchez Vicario
became the first tennis player to compete in five Olympics, losing with Anabel Medina Garrigues in the first round of the women's doubles to seventh-seeded Paola Suarez and Patricia Tarabini.
Henin-Hardenne began nervously and was broken in the first game of the match but soon settled in the blustery conditions and fought back to claim the first set.
She broke in the in the third game of the second and the set then went with serve as Henin-Hardenne eased into round two in 75 minutes.
"Even if I was nervous, I had good feelings on the
court," said the 22-year-old Henin-Hardenne. "I feel finally healthy.
"If I play well or badly, win or lose, that's not the
most important thing. I feel I can do my job again, my
passion, and that's the most important right now."
In the second round she will meet Maria Vento-Kabchi of Venezuela.
Sixth seed Williams took just 57 minutes to reach the second round.
The American said she was happy with her fitness and her game despite having both wrists and her left knee bandaged.
Also through are Japanese eighth seed Ai Sugiyama, 10th seed Patty Schnyder and 11th seed Francesca Schiavone.
Sugiyama had to battle hard before finally seeing off Zheng Jie of China 4-6 6-3 8-6.
Swiss player Schnyder beat Petra Mandula of Hungary 6-3 6-4 while Italian Schiavone overcame Shinobu Asagoe of Japan 6-3