Serena Williams demonstrated why she is the favourite for the US Open despite being seeded 29th as she demolished Bojana Jovanovski in round one.
The American, playing her first match in New York for two years because of injuries, powered through the night session match 6-1 6-1 in 56 minutes.
World number one Caroline Wozniacki earlier produced a commanding display against Spain's Nuria Llagostera Vives.
The Dane won 6-3 6-1 and will next play Arantxa Rus of the Netherlands.
Wozniacki suffered two first-round defeats on her arrival in North America after Wimbledon and was thankful for ending that run with a fourth consecutive New Haven title last week.
"Yeah, I've gotten a couple of losses, but that's what happens," she said.
"I tried a few things that didn't work out but I came back last week and won in New Haven, which was a great feeling.
"I'm number one still and I've just won a tournament, so I'm feeling fine, I'm feeling good."
There was a shock on Louis Armstrong Stadium as former junior number one Simona Halep of Romania beat sixth seed and French Open champion Li Na 6-2 7-5.
Li was crestfallen after a second successive first-round loss at the US Open, saying: "I really wanted to do well after Roland Garros, but it's not easy to do.
"It's always easy to say, but always I lose early. Now I even lose all my confidence on the court. I was feeling, 'Oh, tennis is just too tough for me."'
Williams missed last year's US Open and her lengthy absence from the sport meant she has been seeded down at 29th, but she remains the woman to beat.
Her last match on Arthur Ashe Stadium was the 2009 semi-final defeat by Kim Clijsters, during which Williams verbally attacked a line judge, prompting a hefty fine.
There was no such drama on her return as she had far too much for Jovanovski, overpowering the 19-year-old Serbian to set up a meeting with Michaella Krajicek in round two.
"I'm so happy to be here. I didn't think I would make it," said Williams. "I'm always nervous in the first round and I was nervous out there tonight.
"I think I could have played better. I was just out there."
Fourth seed Victoria Azarenka and 11th seed Jelena Jankovic also progressed on Tuesday, Azarenka beating Sweden's Johanna Larsson 6-1 6-3 and Jankovic defeating Alison Riske of the United States 6-2 6-0.
"There are always things that could have been done better, but I think I had a pretty solid start," said Azarenka, who could face Serena Williams in the third round.
"I'm not interested about that before I go out there," the Belarusian said of that potential match. "We'll talk about it later maybe."
Wimbledon semi-finalist and 22nd seed Sabine Lisicki eased past Alona Bondarenko 6-3 6-3 to set up a second-round meeting with the unseeded Venus Williams.
Germany's Andrea Petkovic, the 10th seed, defeated Ekaterina Bychkova 6-2 6-2, while 16th seed Ana Ivanovic of Serbia beat Ksenia Pervak 6-4 6-2 and Italy's seventh seed Francesca Schiavone battled past Galina Voskoboeva 6-3 1-6 6-4.