Hingis, who has gone without a title since February, posted a 6-2, 6-3 win over Italy's Tathiana Garbin for her 40th match win of the season.

Eighth seed Arantxa Sanchez-Vicario of Spain, the 1995 champion, also advanced to the third round by defeating Japan's Ai Sugiyama, 6-3, 6-3.

Hingis has won three titles this season, but none since capturing consecutive Middle Eastern events in February.

The 20-year-old from Switzerland began her claycourt season with a quarterfinal showing at the Bausch & Lomb Championships. Last month, she reached the final at the Family Circle Cup before losing to American Jennifer Capriati, who beat Hingis in the Australian Open final in January.

Hingis has held the No. 1 ranking since May 22, 2000, but Williams has won back-to-back titles to pull within 691 points of the top spot. Williams, seeded second this week, could overtake her Swiss rival at the French Open, which begins May 28.

Seeded players Kim Clijsters of Belgium and American Chanda Rubin were eliminated in first-round action.

Anne Kremer of Luxembourg surprised the 10th-seeded Clijsters, 6-2, 6-1, and Denisa Chladkova of the Czech Republic upended the 12th-seed Rubin, 4-6, 6-4, 6-4.

In other opening-round play, ninth seed Magdalena Maleeva of Bulgaria got past Kveta Hrdlickova of the Czech Republic, 6-3, 1-6, 6-2; No. 14 Sandrine Testud of France defeated Germany's Marlene Weingartner, 7-6 (7-4), 6-2; No. 16 Barbara Schett of Austria held off Sweden's Asa Carlsson, 6-1, 3-6, 7-5; and No. 17 Meghann Shaughnessy of the United States, who lost to Williams in Sunday's Hamburg final, dumped Russia's Elena Likhovtseva, 6-1, 6-4.

On Wednesday, Williams will face Karina Habsudova of Slovakia, and Capriati will face Yugoslavian teenager Jelena Dokic in second-round matchups.

Also, sixth seed Conchita Martinez of Spain opens defense of her title against German qualifier Martina Muller.

First prize is $175,000.