Top seed Justine Henin wasted little time in reaching the second round of the US Open as she thrashed qualifier Julia Goerges 6-0 6-3 in New York.
Henin did not need to find top gear on day one in New York
Henin, who was beaten in last year's final by Maria Sharapova, needed just 62 minutes to complete the victory.
Venus Williams beat Kira Nagy 6-2 6-1 but sister Serena was made to work hard before winning 6-3 7-5 against German teenager Angelique Kerber.
Third seed Jelena Jankovic and fifth seed Ana Ivanovic were earlier winners.
Jankovic left plenty of room for improvement as she beat Jarmila Gajdosova 6-2 7-6.
It's always good to have some competition in the first rounds
She broke her opponent's serve in the opening game and had few problems taking the first set.
But Gajdosova's raw power helped her find her feet in the second as she battled her way from 5-3 down to 6-5 up.
Jankovic held to force the tie-break, and her experience told as she took the match on her seventh match point.
"I was really nervous, for some reason," said Jankovic.
"The first round of the tournament is always difficult, it doesn't matter if it's a Grand Slam or just a regular tournament.
"I was just feeling a little bit not that comfortable. I wasn't playing well, was struggling out there.
If I do what I do in practice I'll be fine - If I play like I did today, I'm going to be in trouble
"But, you know, it's always good to have some competition in the first rounds, to feel that, so you wake up and you're ready for the next rounds."
Ivanovic of Serbia reached the second round with a 6-1 6-1 win over Aiko Nakamura of Japan.
World number one Henin was not at her best, with a misfiring first serve offering opportunities to her opponent.
"I was a bit concerned the last few days with my shoulder," said the Belgian. "It's getting better but still a little bit scary.
"I don't have a lot of things to say about that match because there wasn't a lot of rhythm. She was serving pretty hard, pretty good, but did a lot of mistakes."
The 25-year-old Serena Williams made 26 unforced errors against Kerber and admitted: "I didn't play well at all."
The eighth seed, nursing a sore thumb in her first match since losing in the Wimbledon quarter-final, added: "She definitely played a tough game but I made a lot of errors.
"I didn't feel I moved my feet well. I felt like I was just flat footed. I felt like I was just heavy. I don't know.
"If I do what I do in practice I'll be fine. If I play like I did today, I'm going to be in trouble."
Meanwhile, 15th seed Dinara Safina overcame Colombia's Catalina Castano 6-2 6-3.