The Dunhill Links is a pro-am, formatted like the Pebble Beach Pro-Am on the PGA TOUR. For the first three days, play will be contested on three courses - the Old Course at St. Andrews (par 72), Carnoustie Golf Club (71) and Kingsbarns Golf Links (72) - before the final round is played on the Old Course.
World No. 5 Vijay Singh shares fourth place with Simon Dyson and 2002 champion Padraig Harrington at minus-9. Singh posted a 2-under 70 at St. Andrews, while Dyson shot 68 at Kingsbarns and Harrington carded a 69 at St. Andrews.
Dredge got off to a hot start with a birdie on the par-4 10th and made it two straight as he also birdied No. 11. The Welshman moved to 11 under as he birdied the par-5 14th. He parred the next five holes around the turn.
Dredge, who won the Omega European Masters last month, collected his fourth birdie on the par-4 second.
He moved to 13 under with a birdie at the fifth, but gave that stroke right back as he bogeyed the sixth. Dredge parred the last three holes to end at minus-12.
'I got off to a good start again and hit some really good shots,' Dredge stated. 'There were a couple of iffy shots later, but I scrambled well and chipping in twice is not something that happens often.'
Edfors stumbled out of the gate with a bogey on the second at St. Andrews. He quickly atoned for that error with a birdie on the third, then drained back-to-back birdie putts from the fifth to move to minus-10.
The Swede kept climbing the leaderboard as he birdied the ninth. Around the turn, he grabbed a share of the lead thanks to a birdie on No. 11.
Edfors, a three-time winner this season, stumbled down the stretch with a bogey on 16 and a double-bogey on the Road Hole, No. 17. He got one stroke back with a birdie at the last to share second.
Schwartzel followed Edfors off the first tee and he parred the first four holes. He picked up his first birdie on the par-5 fifth, then birdied the seventh and ninth to turn at minus-8.
The South African also parred the first four holes of the second nine. He birdied the par-5 14th and closed with a birdie at the last to finish at 10 under.
'I hit 17 greens (Thursday) and probably the same today,' Schwartzel said. 'It gives me more confidence going into the weekend.'
Ernie Els fired a 5-under 67 on the Old Course. He moved into tie for seventh at minus-8 alongside Miguel Angel Jimenez (69 at St. Andrews) as well as Scott Drummond and Mikko Ilonen, who both shot 69s at Carnoustie.
First-round leader Paul Casey is one of seven players one stroke further back at minus-7. Casey stumbled to a 2-over 74 Friday on the Old Course.