European number one Justin Rose fired a flawless 65 to claim a share of the lead after the second round of the Nedbank Challenge on Friday.
Rose, who won the Volvo Masters at the start of November to claim his first Order of Merit crown, carded seven birdies and no bogeys over the daunting Gary Player course at Sun City.
The Johannesburg-born 27-year-old went to the turn in 34 with birdies at the second and eighth and picked up further shots at the 10th, 11th, 13th, 15th and 18th.
On 11 under par he shared the lead with South African Trevor Immelman, who was making the most of his late call-up into the 12-man field.
Immelman, who replaced Sergio Garcia in the £2.2million event, was more inconsistent than Rose but still managed eight birdies and two bogeys to retain a share of the lead.
Home favourite Ernie Els, seeking a fourth title and the £600,000 first prize, lies three off the pace after a 67 which threatened to be much better.
The former Open champion was six under after 13 holes but failed to register any further birdies and bogeyed the 17th to finish eight under.
Sweden's Henrik Stenson is a shot further back on seven under with Australian Adam Scott, joint leader overnight with Immelman, six under after a 71 which saw him drop three shots in the last three holes.
England's Luke Donald, joint second with Rose after an opening 68, could only manage a second-round 71 to slip to sixth place.
South African Charl Schwartzel props up the field on four over.
Collated second-round scores & totals (Rsa unless stated, par 72):
133 Trevor Immelman 67 66, Justin Rose (Eng) 68 65
136 Ernie Els 69 67
137 Henrik Stenson (Swe) 72 65
138 Adam Scott (Aus) 67 71
139 Luke Donald (Eng) 68 71
142 Geoff Ogilvy (Aus) 69 73
144 Rory Sabbatini 76 68
145 Retief Goosen 74 71, Stewart Cink 72 73
146 Niclas Fasth (Swe) 74 72
148 Charl Schwartzel 74 74