Martina Hingis, Venus Williams and Monica Seles all had easy passages into the quarter-finals of the Australian Open.
Four-time champion Seles advanced into the next round when her opponent Anabel Medina Garrigues of Spain retired with an injury.
Medina Garrigues appeared to twist her right knee during a rally when eighth seed Seles was serving at 4-2 in the first set.
The 19-year-old Spaniard was treated by the trainer and attempted to play on but was unable to continue.
Seles will next face second seed Williams, who dismissed the challenge of Bulgarian 13th seed Magdalena Maleeva in straight sets.
Williams looked much more impressive than she had in the opening rounds of the tournament as she came through 6-0 6-3.
"I felt very good - especially seeing as I've been a little bit injured," said Williams, who has been struggling with tendinitis in her left knee.
Three-time champion Hingis reached her seventh consecutive quarter-final in Melbourne when she demolished South African Amanda Coetzer for the loss of just one game.
The third seed took just 44 minutes to secure a 6-1 6-0 victory and set up a last eight clash with unseeded Italian Adriana Serra Zanetti.
"Every game I've played I feel better, more secure in my shots," said 21-year-old Hingis.
"Now I really have the belief that I can go all the way."
Serra Zanetti swept past Slovakia's Martina Sucha in straight sets to make her first-ever Grand Slam quarter-final.
Serra Zanetti has had an injury-plagued career but she said she was delighted to reach the last eight.
"When I was 18 I was in the top 100 but then I had a shoulder problems and a change of coach so it hasn't been easy for me," she said.
"I think I'm playing my best tennis now and I hope it will get better and better."
The Italian, ranked 83 in the world, broke Sucha's serve three times in the first set.
One break in the second was enough to secure the match.
Women's fourth results (Sunday)
(8) M Seles (US) bt A Medina
Garrigues, Spain, 4-2 retired.
A Serra Zanetti (It) bt M Sucha (Svk) 6-1 7-5
(2) V Williams (US) beat (13) M Maleeva (Bul)
6-0 6-3
(3) M Hingis (Swi) bt A Coetzer (SA) 6-1 6-0
Related to this story:
Novak through to last eight
(20 Jan 02 | Australian Open)
Seles through as Garrigues retires
(20 Jan 02 | Photo Galleries)