Englishman Ross Fisher and South African Tim Clark posted five-under-par 68s to equal the course record and move into the overnight South African Airways Open lead.
Swede Henrik Nystrom finished one behind the lead, with compatriot Mattias Eliasson and South African Charl Schwartzel on three-under for joint third.
Teeing off on the back nine, defending champion Clark posted four birdies and an eagle for his round, the only blemish coming with a bogey on his ninth and final hole.
Fisher teed off on the 10th hole and posted five birdies and four pars to draw level with Clark at the turn.
His back nine was not as consistent and he finished with two bogeys at the first and eighth, although he carded another two birdies at the fifth and ninth to go back to five-under.
“I’ve always been strong off the tee, and that helped today,” the Wentworth member explained.
“It gave me the chance to play for the correct side of the green – maybe 20 or 30 feet offline – and let the ball feed in. Because of this, I was able to set my putts up nicely.
“Things were very slow at the beginning. It was hard to concentrate but I just told myself to just be patient and it was nice to end off with a birdie at the 18th.”
Fisher’s best result to date was a fourth at the European Tour’s 2006 Volvo China Open held last month.
He finished 18th on the 2005 Challenge Tour to secure his playing privileges for 2006, and then finished 14th on the European Tour Qualifying School to improve his category listing.
He started playing the game at the age of just three and turned professional in 2004.
Meanwhile, Clark was happy with his round, but spoke of the tough course conditions.
He said: “The course is playing really tough – every hole is demanding and when you hit a bad shot then you’re guaranteed to put down a big number on your card.
“Bogeys are inevitable, it’s just a case of avoiding the double bogeys with good course management. You also can’t attack this course, you need to play safe most of the time.”
Clark has officially joined the European Tour and will play at least the minimum 11 tournaments required during the 2006 season.
A victory on Sunday would cap a fine year for the South African, who celebrates his 30th birthday this Saturday.
He picked up £1.3m (€1.9m) on the PGA Tour, won the Scottish Open, finished third in the US Open and rose more than 50 places on the world rankings.
South African-born Justin Rose carded a one-over-par 74 for joint eighth.
Rose explained: “I think my bogey on the first hole summed things up for me but I enjoyed grinding it out today.
“The back nine was much better and to finish anywhere near level par on day one is good. I’m looking forward to tomorrow.”
Damien McGrane and David Higgins are best plpace of the Irish at two over. Stephen Browne is at five over and Gary Murphy is at nine over.