Australian Open, Melbourne
Venue: Melbourne Park Dates: 17-30 January
Coverage: Watch on BBC TV, Red Button, BBC Sport website (UK only) & Eurosport; listen on BBC 5 live sports extra and online; text commentary online;
Clijsters was not at her best against Makarova
US Open champion Kim Clijsters reached the last eight at the Australian Open following a 7-6 [7-3] 6-2 victory over Russia's Ekaterina Makarova.
The number three seed took the first set on a tie-break after both players had broken each other earlier on.
The Belgian then broke Makarova in the third and seventh games of the second set before sealing victory on her own serve after midnight in Melbourne.
Earlier, world number two Vera Zvonareva beat Iveta Benesova 6-3 6-1.
The Russian, a semi-finalist in 2009, edged a scrappy first set but was in cruise-control in the second to come through in one hour 16 minutes.
She will play Petra Kvitova for a last-four spot at Melbourne Park, while US Open champion Clijsters will play Poland's 12th seed Agnieszka Radwanska, who saved two match points before coming through against China's Shuai Peng 7-5 3-6 7-5.
Clijsters took 56 minutes to win a scrappy first set and later explained why she found it difficult to find her rhythm early on.
"She was unpredictable," said one of the tournament favourites. "I had to get a feel for it.
"In the second set I started being a bit more aggressive. I had to really step it up and finish it off."
The 2004 finalist's win owed a lot to the unforced errors made by her opponent - 21 in the first set and then 15 in only eight games of the second.
Clijsters was also seen to take anti-inflammatory pills for a tight hamstring during the second set, but that did not seem to affect the performance of the former world number one.
Meanwhile, Zvonareva, 26, was broken early in the first set by Czech Benesova and trailed 4-2 before recovering to win the next four games and take a close opening set.
The second seed had few problems in the second and breezed through with 21 winners and four aces as she broke her opponent's serve five times.
"I was happy at the way I was able to come back when I was 4-2 down in the first set," said the Russian, who is still looking for her first Grand Slam title having been runner-up at last-year's Wimbledon and US Open.
On facing Kvitova, a surprise semi-finalist at Wimbledon last year, Zvonareva added: "She's had a great run here and beaten Sam Stosur and now Flavia so I know how tough that match is going to be.
"I had a little bit of a slow start to the tournament but I have picked it up in every match. That's how you want it to be at a Grand Slam."
Kvitova, the world number 25 who defeated Stosur in round three, fought back to see off Flavia Pennetta 3-6 6-3 6-3.
The 20-year-old Czech struggled with her serve as she lost the first set but steadied her game to level the match.
Pennetta, the 22nd seed for Italy, was broken to trail 4-2 in the decider as Kvitova piled on the pressure to eventually ease through on Hisense Arena.