Branden Grace and Chase Koepka led the way at the BMW SA Open Championship Proudly hosted by the City of Ekurhuleni after composed first round displays at Glendower Golf Club.
Koepka hit one eagle, seven birdies and two bogeys to set the seven under par target earlier in the day before home favourite Grace rattled in three eagles of his own to finish the day as co-leader.
The American opened his round with a bogey but struck back immediately with an eagle at the next before birdies at the fifth, sixth and eighth propelled him to four under at the turn.
A dropped shot at the tenth brought him back to three under before three successive gains from the 12th put Koepka at the top alongside English pair Chris Paisley and Matt Wallace at six under par and when the World Number 336 birdied the par four 16th, he took the lead.
The putter was really hot on the front nine - Chase Koepka
Koepka rescued a par at the penultimate hole after his lengthy putt reached five feet and the 23 year old almost extended his lead to two shots on the last but his putt from the fringe missed the left edge of the cup.
"It was great," the European Tour rookie said. "I think I played flawless, except for the second shot on the first hole. I hit a poor shot there and saved it with a 12-footer for a bogey. I made eagle on the second hole and kind of kept it going from there.
"Inside 150 yards, I was really good today. I didn't have too many shot from inside 150, but every one that I had, I was hitting them close. The putter was really hot on the front nine and then I had a bunch of short putts on the back nine which helped a little bit.
Grace replicated Jeff Winther's final round from last year's tournament when he recorded three eagles at the second, eighth and 15th - the last time a player has done this in a single round - in his score of 65.
The eight-time European Tour winner started with a streak of par-eagle-birdie to race to three under but bogeys at the fourth and sixth put him back to one under.
However, the 29 year old gained a stroke at the seventh and then recorded his second eagle at the par five eighth with a lovely putt from 25 feet and when he birdied the tenth, he moved to five under.
The scoring settled down as the South African parred the next four but still had time to hole a tricky eagle putt from 20 feet at the 15th to join the American at the top of the leaderboard, where he is hoping to become just the second golfer to secure South Africa's three most prestigious events with victory in Ekurhuleni, after player host Ernie Els.
Defending champion Graeme Storm could only muster a three over par 75, with former Masters Tournament champion Charl Schwartzel battling back from one over at the turn to reel in five birdies and one bogey to end the first round on three under par.
Els finished on one under for the day, while compatriot and two-time US Open champion Retief Goosen rolled in five gains on his way to a score of 69.
Paisley is just one shot adrift in sole second place after briefly taking the lead midway through his round of 66 in South Africa, rattling in seven birdies and one bogey.
Former Amateur Championship winner Bradley Neil was among a quartet of players to finish on five under following a rollercoaster round of 67, with South African duo Erik van Rooyen and Richard Sterne and Spain's Nacho Elvira.
Wallace, who led the charge for most of the morning, found himself at four under alongside six South Africans Jacques Blaauw, Ulrich Van den Berg, Jacques Kruyswijk and Tyrone Ferreira and amateur pair Garrick Higgo and Kyle McClatchie, with France's Adrien Saddier and Denmark's Winther rounding off the 68 scoring group.