Leading contenders Maria Sharapova and Kim Clijsters overcame windy conditions at Flushing Meadows to reach the third round of the US Open on Wednesday.
Clijsters survived an alarming early slump to beat Fabiola Zuluaga.
The Belgian let a 4-0 lead slip with the loss of five straight games and faced a set point in game 10, before recovering to win 7-5 6-0.
Sharapova's power then proved too much for Madagascar's Dally Randriantefy in a quick 6-1 6-0 victory.
Clijsters will face 30th seed Ai Sugiyama next, while Sharapova meets Julia Schruff.
"It was very tough out there and she got used to it a little bit more than I did," said Clijsters.
"I lost my footwork and wasn't aggressive enough.
"But after that in the second set, I knew I just had to keep going for the lines and not think about the wind too much."
Sharapova needed just 49 minutes to beat Randriantefy, and then defended her hectic schedule of practice and fulfilling sponsors' commitments.
"There are going to be times where, especially before a Grand Slam, you need to set back some time and do these things for the sponsors," she said.
"I think in the morning I was doing the Today Show, being all glamorous. Then I'm back on the court after three hours and I'm working hard.
"This is where I feel I really belong."
The biggest surprise of the day was the defeat of 18th seed Ana Ivanovic, who lost 3-6 7-5 6-1 to Maria Vento-Kabchi.
And Israel's Shahar Peer edged out Russian 33rd seed Vera Douchevina 7-5 3-6 6-3.
Ninth seed Nadia Petrova of Russia had no such problems, powering past Japan's Aiko Nakamura 6-2 6-0.
Earlier, 26th seed Nicole Vaidisova of the Czech Republic had an impressive 6-3 6-0 win over China's Zheng Jie.
The 16-year-old goes on to face Croatia's Ivana Lisjak, who defeated Ekaterina Bychkova - conqueror of champion Svetlana Kuznetsova in round one - 7-5 6-1.