America's Venus Williams and Chanda Rubin crashed out of the first round women's doubles tennis after a surprise three-set defeat to Chinese pair Li Ting and Sun Tian Tian on Monday.
The eighth-seeded duo beat their American opponents 7-5 1-6 6-3.
Venus, who won gold in Sydney with her sister Serena four years ago, had never played doubles with anyone other than her younger sister.
Serena was forced to withdraw from The Games because of a knee injury.
Earlier, Russia's Anastasia Myskina eased into the second round of women's singles with a 6-0 6-1 victory over Italy's Magui Serna.
The French Open champion showed no effects from a rib injury which forced her to miss a tournament in Poland last week.
France's Second seed Amelie Mauresmo also booked her place in the next round with a 6-1 6-4 victory over Spain's Conchita Martinez.
But Russia's fourth seed Elena Dementieva lost out to Australia's Alicia Molik in three sets.