Kim Clijsters turned in a mixed performance as she beat Justine Henin 2-6 6-2 6-3 to book her place in the quarter-finals at Wimbledon.

Clijsters, who last played here in 2006 when she lost to Henin in the semi-finals, edged a close battle against her compatriot, who suffered a fall in the opening set and appeared to damage her right wrist.

After the first two sets were shared in just under an hour, Clijsters made the crucial breakthrough in game eight of the decider and Henin, whose usual fearsome baseline game let her down, had no answer as the eighth seed wrapped up the win when her opponent netted a forehand return.

Clijsters will play 21st seed Vera Zvonareva for a place in the semi-finals; the Russian progressing when Serbia's Jelena Jankovic retired whilst trailing 6-1 3-0.

The fourth seed received treatment for an injury to her back and looked ill at ease throughout the match in the glorious sunshine on Court 12.

Zvonareva raced to the opening set in 24 minutes and claimed two breaks in the second when Jankovic had a medical timeout.

She returned for three more points before strolling to the net and offering her hand after 43 minutes of play.

Five-times champion Venus Williams was given a testing workout in the blazing sun before booking her place in the quarter-finals with a 6-4 7-6(5) win over Australia's Jarmila Groth.

One break of serve was sufficient for the American second seed to take the first set after 35 minutes on Court Two but her Slovak-born opponent fought back determinedly in the second.

She served for the set at 5-4 and 6-5 but on each occasion Williams thwarted her, and Groth did well to recover from 4-0 down in the tiebreak before going down 7-5 when the Australian netted a mid-court forehand after an hour and 37 minutes.

She will play Tsvetana Pironkova for a place in the semi-finals, after the unseeded Bulgarian dispatched 11th seed Marion Bartoli 6-4 6-4.

China's Li Na kept the flag flying for Asia in the women's singles when she disposed of Polish seventh seed Agnieszka Radwanska 6-3 6-2.

Li, into the quarter-finals for the second time, used her bludgeoning ground-strokes to keep Radwanska pinned to the back wall for much of their match on Court 18.

The ninth seed converted the only break point of the first set to claim the lead in just 30 minutes, and sealed victory when she smashed away an easy overhead after 67 minutes.

She will play either defending champion Serena Williams or Russian 16th seed and 2004 winner Maria Sharapova for a place in the semi-finals.

Denmark's third seed Caroline Wozniacki crashed out of the tournament when she was outplayed 6-2 6-0 by Czech Petra Kvitova.

Kvitova, who lost in the first round on her only two previous campaigns at the All England Club and is now in the quarters, put in a violent display of hitting on Court Two and Wozniacki was left aghast looking for answers.

The world number 62 hit 14 crunching winners en route to the first set in just 24 minutes and it was all over when Wozniacki netted a forehand just 22 minutes later.

Kvitova will play Estonia's Kaia Kanepi for a place in the semi-finals, after the qualifier beat Czech Klara Zakopalova 6-2 6-4.