Sun City - Retief Goosen took a one-stroke lead over Masters champion Angel Cabrera at the Nedbank Challenge, shooting four-under 68 in the second round on Friday.
Goosen opened with three birdies on his first four holes.
The South African made three more birdies at the Gary Player Country Club but also had two bogeys for a seven-under 137 overall.
Cabrera had the low round for the day with a 67.
Defending champion Henrik Stenson (68) and Robert Allenby (70) are tiled with the Argentine in second place.
Rory McIlroy, who complained of stomach pain, shot a four-over 76 and is last in the 12-man field at 149.
Scores after the second round:137 - Retief Goosen (RSA) 69-68;
138 - Robert Allenby (AUS) 68-70, Angel Cabrera (ARG) 71-67, Hendrik Stenson (SWE) 70-68;
141 - Tim Clark (RSA) 69-72, Hunter Mahan (USA) 70-71;
142 - Ross Fisher (ENG) 73-69, Robert Karlsson (SWE) 70-72;
143 - Luke Donald (ENG) 72-71;
146 - Nick Watney (USA) 73-73;
147 - Richard Sterne (RSA) 72-75;
149 - Rory McIlroy (NIR) 73-76.