Leader: -12 B Koepka
-10 A Scott; -9 J Rahm, R Fowler, G Woodland
Selected: -8 T Woods, S Cink, J Day, J Thomas, S Lowry, C Schwarzel
-7 F Molinari; -5 E Pepperell, I Poulter, M Wallace, J Rose
-3 T Hatton; -2 R McIlroy, T Fleetwood, R Knox; level R Fisher
Round four live coverage from 19:00 BST
Six players level in the chasing pack on eight under par - Tiger Woods, Justin Thomas, Adam Scott, Rickie Fowler, Gary Woodland and... Stewart Cink! When did he join the party?
Three birdies since the turn for the American, following a solitary bogey, and he's four under for the day.
Another six players a further stroke off the pace, with Francesco Molinari and Jason Day among them.
R Fowler -8 (14), A Scott -8 (15)
Rickie Fowler's dropped further off the pace. The American can only make bogey at the 13th and then fails to roll in his birdie putt at 14. Back to eight under par - five off the lead.
Adam Scott is now out in second place on his own, but still fours shots adrift of Brooks Koepka.
Hang on... that was brief, the Australian cards a five on the par-four 15th. Make that lead FIVE for Koepka!
Alex Miceli
US golf reporter on BBC Radio 5 live
He's played a lot of golf today but putting is more mental than physical. If you're in contention at a major championship you cannot miss four footers.
T Woods -8 (17)
Un. Be. Liev. Able.
Woods blinks for the first time in a while, pushing a four-foot putt onto the left edge and lipping out.
That would have moved him into tied second with Adam Scott on nine under.
Woods grabs his putter with both hands, one on the head, one on the grip, probably thinking about throttling it.
T Woods -8 (16)
Here we go then... Tiger for eagle... if this goes in you'll hear the roar back in the UK.
"In the hooooooole!" is inevitably heard as soon as his putter face hits the ball, which Tiger has laced towards the can.
He can't be accused of not having a go. Unfortunately for the 14-time major winner it doesn't move from the top-right line. Shouldn't be too much bother knocking in the birdie putt, however....
Image source, Getty ImagesB Koepka -13, G Woodland -8, K Kisner -7 (13)
Tricky for Brooks Koepka after over-hitting the green a touch, but he dinks on smartly to leave himself with a makeable par putt.
Gary Woodland has suddenly rediscovered his birdie form, has he? Nope, he can't make it two on the bounce as an effort on 13 whistles narrowly by.
Koepka, meanwhile, confidently drowns his par-saver from 10 feet to maintain his lead - a couple of important saves for the US Open champion.
T Woods -8 (16)
Just the 243 yards to go for Tiger Woods on the par-five 17th. And he's got an iron in his hand.
A sweet swish leaves the galleries purring, Woods likes it too as he walks after it. A tell-tale sign.
Stick on your best shoes, Tiger - you're grooving on the dancefloor. An eagle putt from around 17 feet awaits...
B Koepka -13, K Kisner -7, G Woodland -8 (12)
Triple bogey a few moments ago for Gary Woodland, but he's just clawed one of those strokes back at the 12th. No such luck for Kevin Kisner, who makes it bogey-bogey.
Brooks Koepka, cool as you like, tucks away for another par to keep that four-stroke lead.
Image source, Getty ImagesI Poulter -5 (F)
Karen Stupples
Former Women’s British Open champion on BBC Radio 5 live
Ian Poulter should be on the Ryder Cup team. He has that scrapping mentality and he wants to stick it to the Americans. You need that in the team.
Poulter mixed five birdies with three bogeys today for a two-under 68.
B Koepka -13, K Kisner -8 (11)
Kevin Kisner's round is in danger of quickly slipping away, with the American spraying his approach right of the green and into a bunker lurking down below.
Long bunker shot for the American, he draws on a touch of spin as it digs in around the fringes of the green.
Brooks Koepka's given himself a lengthy birdie putt. Straight as an arrow, he zips it pin-bound, but it just clips the cup and trickles on by.
T Woods -8 (16)
Tiger on the 17th tee... danger lurking on the right... he smashes it down the left and cuts it back onto the fairway - 103 feet of curve on that drive. Possibly a chance of reaching the green in two on this par five...
R Fowler -9 (12), A Scott -9 (13)
Rickie Fowler and Adam Scott are hanging around, trying to keep pace with leader Brooks Koepka. Fowler dusts off that bogey at the 10th with a couple of pars while Scott is still yet to drop a shot today.
B Koepka -13 (11)
Keep expecting those Koepka drives to come down with some of yesterday's hail on them - another thunderbolt down the 12th that pitches just before the slight dogleg to give him a look at the pin.
Image source, Getty ImagesR McIlroy -2 (F)
Iain Carter
BBC Sport golf correspondent on BBC Radio 5 live at Bellerive
Rory McIlroy finishes up on 18 with a par and he's at two under. He's not going to get his hands on the Wanamaker Trophy this week and it's a fourth year without a major for the Northern Irishman.
It was a course set up for McIlroy, wide fairways, soft greens but he's not been able to take advantage.
Woods -8 (16)
Up on the 16th... Tiger Woods with another birdie chance.
Forty feet stands between the 42-year-old American and the hole... he drills it up the shadowy path, eyes fixed firmly on the ball as it rolls towards the can.
The crowd like it... willing it to drop. But it runs out of steam and ends up short. Tiger closes his eyes and raises his head skywards, while tapping his bonce with his putter. That's what frustration looks like.
Eight pars on the trot for Woods, keeping him five adrift of the leader Koepka.
Image source, Getty Images-13 B Koepka (11)
Selected Others
-9 A Scott (13) R Fowler (11)
-8 T Woods (15) K Kisner (11)
-7 G Woodland (10)
-5 E Pepperell (F*) I Poulter (17) M Wallace (16) J Rose (14)
-2 R McIlroy (F)
B Koepka -13, K Kisner -8, G Woodland -7 (11)
Good save from Brooks Koepka. After a slightly wayward tee shot and then having overhit the green, he scrambles back with a neat chip and solid putt for par at the 11th - he's number one on the scrambling list this week.
Kevin Kisner, sunglasses and baseball cap firmly on like a spoof Hollywood cop, drops further away from the lead with a bogey.
T Woods -8 (15)
Iain Carter
BBC Sport golf correspondent on BBC Radio 5 live at Bellerive
It's been the story of the back nine for Tiger. He's created chance after chance after chance but nothing has dropped.
B Koepka -13 (10)
So Brooks Koepka's closest challengers are currently Adam Scott, Rickie Fowler and Kevin Kisner - all four strokes off the pace.
Koepka has found some rough at the 11th, he's playing over the water and overcooks it a touch as it kicks on beyond the flag and down the bank at the other side of the green.
B Koepka -13, G Woodland -7, K Kisner -9 (10)
Amid the sandy madness surrounding Gary Woodland, Brooks Koepka remarkably fails to roll in a 10-footer and instead prods in for a par that keeps him at 13 under par.
Woodland, meanwhile, finally makes it down in SEVEN for a triple bogey.