ROME (AP) - Martina Hingis dominated an impatient Serena Williams right from the start today, reeling off 16 of the first 17 points en route to a straight-set victory in the Italian Open quarterfinals.

Hingis, the defending champion and top seed, gave the sixth-seeded American a 6-2, 6-2 lesson in clay-court tennis on a windy afternoon.

Williams has been on a roll this season and had dropped just eight games in two matches here, but got into trouble Friday by trying to force the action, compiling more than two dozen unforced errors in the 62-minute encounter.

``I didn't make any shots out there. You could probably count the number of shots I made - two or three. She kept a lot of pressure on me,'' Williams said.

``She didn't really win. I gave it to her. I made so many errors, it was really, absolutely absurd.''

She had reached the finals of the last three events she had played, winning two for the first titles of her career.

But Hingis, already a five-time Grand Slam tournament champion at the age of 18, kept the American off-balance with deep shots to the corners.

``I just didn't miss. I was very focused, and didn't let her back in the game. I didn't give her any free points,'' Hingis said. ``And I just didn't give her the chance to kill me. I guess I made her kill herself.''

The world's top-ranked player jumped out to a 4-0 lead while dropping just one point - on her own double fault in the second game. Otherwise, Williams did not get on the scoreboard until hitting a forehand winner in the fifth game. As the ball flew past Hingis, Williams raised her arms in mock celebration.

``It's weird for me to walk into a match and not be able to do things I've been able to do for so long,'' Williams said.

Hingis, who's lost a total of 11 games through three matches in Rome, could face another Williams next.

Third-seeded Venus Williams, Serena's older sister, played Dominique Van Roost of Belgium in a later quarterfinal.

``There is another Williams on the way. Beating the whole family all the time is not easy,'' Hingis said with a laugh.

Venus Williams and Hingis each have won three titles in 1999, tying for the tour lead.

Amelie Mauresmo ended Sylvia Plischke's string of upsets, overpowering the unseeded Austrian in straight sets to reach the semifinals.

Mauresmo, at 19 a surprise finalist at the Australian Open in January, won 6-2, 6-3 in exactly an hour.

The 10th-seeded Frenchwoman will meet Mary Pierce in Saturday's semifinals.

Pierce, the 1997 Italian Open champion and seeded fourth this year, advanced by beating another French player, No. 8 seed Sandrine Testud, 6-4, 7-5.