Top seed Serena, who has yet to drop a set, clubbed Russian Elena Dementieva 6-2, 6-2 on Centre Court and she was quickly joined by sister Venus, fellow Americans Jennifer Capriati and Lindsay Davenport and second seed Kim Clijsters of Belgium.

Barring Serena's path to the semis is eighth seeded Capriati who beat Russian 10th seed Anastasia Myskina 6-2, 6-3.

Serena, who is bidding for a fifth Grand Slam title in six events, romped into a 4-0 lead in just nine minutes but then her hitting became somewhat erratic and Dementieva gratefully held before a barrelling forehand which wrong-footed the American saw her break back in the sixth game.

But the champion broke back immediately to put the pressure right back on the 21-year-old from Moscow and wrapped up the set in only 22 minutes.

Serena had a trio of break points at the start of the second set, missed all three then squandered three more before netting from close range to fall a game behind.

She then had to recover from 0-30 to bring through her next serve but the 21-year-old's extra power gave her another gear as she raced to three more break points before world number 16 Dementieva chopped into the net to drop serve to love.

Dementieva pulled out a neat stop volley as she saved one of three break points with Serena leading 4-2 but a crunching forehand from the favourite left the Russian on the verge of defeat.

Serving for victory Serena, who powered down six aces, raced to triple match point, double faulted and looked disgusted with herself.

She then glared as a crosscourt drive landed wide but then accepted the win third time round when Dementieva sent a double-fisted effort wide at full stretch after 51min.

Venus avenged her shock French Open defeat by Vera Zvonareva to storm into the last eight for the sixth straight year.

Heavy overnight rained had delayed the start of the match for an hour and Williams appeared determined not to be kept waiting around a minute longer than necessary as she raced to a 5-0 lead in the opening set.

Zvonareva put up more resistance in the second set but she was unable to prevent the American from completing a 6-1, 6-3 victory in exactly an hour.

Williams, bidding to add a third Wimbledon crowd to her 2000 and 2001 titles at the All England Club, now faces an all-American quarterfinal clash against 1999 champion Davenport.

Williams, seeded fourth, has yet to drop a single set and conceded just 16 games in her four matches.

Ominously for Davenport, there has not been the slightest hint of Venus being constrained by the abdominal muscle injury that contributed to her defeat by Zvonareva at the same stage in Paris a month ago.

Then, the young Russian was able to dictate the pace of the play, dragging Venus from one side of the court and forcing her into an uncharacteristically high level of unforced errors.

The pattern of Monday's opening set could not have been more different with Venus slipping into a power-hitting groove that Zvonareva was simply unable to live with.

The young Russian had been on court for a full 20 minutes before she claimed her first game and even then it was a lapse of concentration from her opponent, whose two unforced errors allowed her to claim the sixth game of the opening set.

Zvonareva briefly looked like making a fight of it by breaking Williams' serve to level things up at 2-2 in the third and then holding to lead.

Rather than the signal for a fightback however that proved to be a trigger for Venus to step up a gear again and she reeled off the next four games to complete her victory.

Former champion Davenport swept through with a crushing 6-4, 6-1 defeat of Japan's Shinobu Asagoe.

Davenport broke serve in the opening game of the match and wrapped up the first set in 29 minutes under a brooding grey sky.

The fifth seed stepped up a gear in the second, winning it in just 17 minutes before the rain, which had delayed the start of the match, started to fall again.

"We were really eager to get out there and get back in again, just in case its started raining," Davenport said afterwards.

Asagoe, who beat ninth seed Daniela Hantuchova in the second round last week, had no answer to the American's searing groundstrokes and failed to take a single point off Davenport's serve in the second set.

"I think my serve is getting better," said Davenport. "I've served well here and I haven't been broken much in the last few matches."

Asked about her clash with the elder of the Williams sisters, she said: "I'm going to just go out there and try to be aggressive, and try to serve well above all."

Belgian second seed Clijsters left personal friendship to one side and bludgeoned doubles partner Ai Sugiyama of Japan 6-3, 6-2 in her fourth round match.

Clijsters quickly settled into her rhythm after an hour's rain delay on court one and her crunching forehand proved too much for Sugiyama, the 13th seed.

The 20-year-old Belgian needed only 25 minutes to take the first set and took a minute less to wrap up the second, sealing her 49-minute victory with a simple forehand volley.

The 2001 Wimbledon quarterfinalist faces a last-eight meeting with Italy's Silvia Farina Elia or Argentine Paola Suarez.

Clijsters win was her 50th singles victory of the year. The last player to reach their half-century so early in the season was Martin Navratilova in 1982.

She is due back on court later on Monday with Sugiyama in the third round of the women's doubles.