Australian Robert Allenby and American Jerry Kelly made the early running after a spectacular storm delayed the start of this year's Nedbank Challenge at the Gary Player Country Club at Sun City.
Allenby, whose last-hole heroics helped the International team tie with the United States at the Presidents Cup last weekend, parred the first hole, but then made birdies at the second and third and fourth to move to three under and into the lead.
Kelly confirmed his status as a dark horse in the tournament with birdies at the first two holes. A group of players, including world number two Vijay Singh and 2001 winner Sergio Garcia, were a shot behind at one under par.
Play was supposed to start at 8:40 a.m. (Irish time), but was delayed by a sudden downpour and thunderstorm.
Defending champion Ernie Els made a solid par at the first hole and is seen as the major threat in this tournament, having won this event in three of the last four years.
Darren Clarke was level par after two holes while Padraig Harrington was one over after three holes.
With a first prize of more than stg£700,000, the richest prize in golf, there is more than enough motivation for the select 18-man field.