On the men's side, No. 6 Tim Henman of Britain -- the highest remaining seed -- will clash with Jonas Bjorkman of Sweden.

The second-seeded Williams looks to avoid another loss to No. 13 Magdalena Maleeva of Bulgaria.

Known for dominating most of her opponents, the 21-year-old American has lost two of her three meetings with Maleeva, including a straight-sets ouster at last year's Nice Indoor event.

The reigning Wimbledon and U.S. Open champion, Williams on Friday slipped by No. 32 Daniela Hantuchova of Slovakia, as she continues to struggle with tendinitis in her left knee. Maleeva, 26, will make her first appearance in the round of 16 here since 1994.

By contrast, the third-seeded Hingis has dominated her all-time series with her fourth-round opponent, No. 15 Amanada Coetzer of South Africa.

The Swiss star and three-time Australian Open titlist has won seven of their nine career meetings. Hingis, in fact, dropped just four games in their last meeting at the 2000 Ericsson Open.

Coetzer has known success at Melbourne Park, reaching the semifinals in 1996 and 1997.

Meanwhile, eighth-seeded Monica Seles will play her first career match against Spanish teenager Ana Isabel Medina Garrigues.

A four-time winner of this Grand Slam event, Seles has reached the quarterfinals in her six previous appearances here.

The 28-year-old American will look to extend her WTA Tour winning streak to 17 matches. Seles captured her final three events of 2001.

Medina Garrigues will be competing in the fourth round of a Grand Slam event for the first time in her career.

In a fourth-round contest between unseeded players, Slovakia's Martina Sucha faces Italy's Adriana Serra Zanetti. Sucha took their only previous meeting at the 2001 Bratislava Indoors.

In the men's draw, Henman will try to advance to his first Grand Slam quarterfinal outside of his own country. A three-time Wimbledon semifinalist, Henman has stumbled in the fourth round here each of the last two years.

The last British player to reach the last eight of the Australian Open was John Lloyd in 1985.

Additionally, Bjorkman has defeated Henman four times in their six career encounters.

A semifinalist at the 1997 U.S. Open, Bjorkman knocked off seeded foes in the previous two rounds -- No. 24 Thomas Enqvist of Sweden in the second round and No. 12 Guillermo Canas in the third.

Prior to this tournament, Bjorkman had conquered a seeded player at the Australian Open just once in eight attempts.

Another Swede will be looking to advance to the quarterfinals. No. 16 Thomas Johansson meets unseeded Adrian Voiea, who will attempt to become the first Romanian to make the last eight here.

Both players have reached the fourth round of the Australian Open for the first time.

Johannson achieved a career-high ATP ranking of 14 last year after winning consecutive grasscourt titles at Halle and Nottingham.

Voinea won back-to-back five-set matches against Frenchman Julien Boutter and American Taylor Dent to advance to the last 16.

In other men's action, No. 26 Jiri Novak of the Czech Republic looks to avoid a fourth defeat in his fifth career match against unseeded Dominik Hrbaty of Slovakia.

Chilean qualifier Fernando Gonzalez will take on unseeded Austrian Stefan Koubek.