Use audio icons to listen to BBC radio commentary
Group One: Durham v Essex; Warks v Notts; Worcs v Derbys
Group Two: Leics v Middlesex; Surrey v Glos
Group Three: Lancs v Yorks; Sussex v Northants
Gloucestershire 158 v Surrey 495
Miles Hammond's superb innings comes to a close as he's caught off the bowling of David Moriarty for 77.
Moriarty finishes with figures of 6-60, his fourth consecutive five or more wicket haul.
Gloucestershire trail by 315. Surely they'll be asked to bat again.
Derbyshire 270, Worcestershire 421
Worcestershire do, in fact, enforce the follow-on. A slight surprise that.
But Derbyshire have been reinserted and will have another go in 10 minutes' time.
Middlesex 295 & 190-8 v Leicestershire 136
It's a five-for for Chris Wright as the Leicestershire man bowls Ethan Bamber for one.
Middlesex are still favourites with a lead of 349. But Wright has given his side a chance today.
Derbyshire 270, Worcestershire 421
Derbyshire are bowled out 151 runs behind.
Dillon Pennington gets his fourth wicket as last man Dustin Melton edges and Tom Fell, who dropped Matt Critchley on 10 earlier, this time clings on to his next chance.
Pennington's figures of 4-44 are his best to date in first-class cricket - in the 20th match of his so far short career
Critchley is left high and dry on 81- his first half century in six innings after that fabulous early-season run of five successive 50-plus scores.
Will Worcestershire enforce the follow-on?
Gloucestershire 153-9 v Surrey 495
Wickets to tell you about at the Oval.
Youngster Will Jacks makes the breakthrough, claiming his maiden first-class scalp bowling Matt Taylor for 12.
Before Daniel Moriarty completes his five-for, bowling David Payne for one.
Gloucestershire trail by 320. Expect a follow-on.
Middlesex 295 & 179-7 v Leicestershire 136
And two more wickets to tell you about from Grace Road as Chris Wright takes a fourth, pinning Martin Andersson in front for four.
Ben Mike follows up in the next over, dismissing Peter Handscomb (36) who edges to the keeper.
Sussex 175 & 298 v Northants 256
Oh no. Tom Taylor pins Henry Crocombe leg before and Jamie Atkins is the last man in with captain Ben Brown five away from a 19th first-class century.
The 32-year-old goes big, but not quite big enough and is caught at long on for 95.
Simon Kerrigan finishes with figures of 5-70. Northamptonshire will need 217 to win.
Derbyshire 264-9, Worcestershire 421
Alzarri Joseph makes it two wickets in successive overs.
This time he removes Sam Conners for 4.
It's far from certain that Pears skipper Joe Leach would actually make them follow on, even if they didn't make that magic mark of 272.
The modern trend is to waive the right, bat on and build a bigger lead - and not have to bat last on a wearing track. But it would be comforting for Derbyshire not to have that option taken out of their own hands.
Matt Critchley is the key man on 78. Last man for Derbyshire is Dustin Melton.
Derbyshire 261-8, Worcestershire 421
Derbyshire still need a further 11 runs to get past the follow-on target at New Road. But they've lost another wicket.
Ben Aitchison was adjudged leg before wicket to Alzarri Joseph.
It's only the West Indian's 12th scalp in six games since signing for Worcestershire in what is scheduled to be his final game.
Matt Critchley remains on 77, now joined by Sam Conners.
Sussex 175 & 297-8 v Northants 256
A crucial 65-run partnership is ended as Jack Carson is eventually pinned lbw by Simon Kerrigan for 35.
Henry Crocombe is the new man in, he joins Ben Brown who's on 94 not out.
Sussex's lead is 216 by the way.
Yorkshire 159 & 1-0, Lancashire 509-9 dec
Lancashire paceman Tom Bailey gets the Yorkshire second innings underway.
With 350 needed to make the hosts bat again, their first run is a leg bye off an opening Bailey maiden.
It's a long road ahead for Adam Lyth and Tom Kohler-Cadmore.
Derbyshire 250-7, Worcestershire 421
Derbyshire lose their seventh wicket at New Road as Alex Hughes is caught behind off Dillon Pennington - a third victim for the Pears paceman.
The visitors still need a further 22 to avoid being asked to follow on.
With in-form Matt Critchley well set on 73, they should do that
Middlesex 295 & 172-5 v Leicestershire 136
Another Leicestershire wicket to tell you about as Sam Evans dives superbly to catch a John Simpson pull shot close in.
It's a third wicket of the innings for Chris Wright. Middlesex lead by 331.
Warwickshire 341 & 10-0, Notts 297
Warwickshire openers Will Rhodes and Rob Yates are back out there at Edgbaston, intent on building on their side's 44-run first-innings lead.
Sussex 175 & 288-7 v Northamptonshire 256
Ben Brown moves on to 87 with another well-timed boundary.
It also takes Sussex's lead past the 200 mark. Not a lead of Lancashire proportions but Northamptonshire may be starting to get nervy.
Mahmood run out 0 (Lancs 509-9 dec, Yorkshire 159)
Saqib Mahmood is run out - and Lancashire skipper Dane Vila promptly declares. The lead is 350.
Josh Bohannon ends on 127 not out - the second first-class century of his career.
The Lancashire innings did not come to an end until the third ball of the 174th over.
Home scorer Chris Rimmer tells BBC Radio Lancashire's Scott Read that it's the first time since 2005 that the Red Rose have batted more than 170 overs in an innings.
Let's see how Yorkshire can respond after a quick shower.
Bailey b Hill 12 (Lancs 504-7, Yorkshire 159)
Tom Bailey lifts George Hill into the stand for a big six to take Lancashire past 500 - but Hill then gets his revenge a couple of balls later when Bailey goes for a repeat and loses two of his stumps.
The lead is now 341.
Lancashire 490-7, Yorkshire 159
Danny Lamb holes out to long off for 61.
It's a first wicket at last for England spinner Dom Bess in his 43rd over of toil at Old Trafford.
It's also Yorkshire's first wicket today in two hours and 39 minutes of cricket.
Warwickshire 341, Notts 297
Warwickshire's England spinner Danny Briggs wraps up the Nottinghamshire innings as he takes the wicket of fellow spinner Liam Patterson-White.
It's Briggs' second wicket and a third clean pouch of the innings for Bears wicketkeeper Michael Burgess.
Group One leaders Notts just miss out on a third batting point - and trail the Bears by 44 on first innings.
Derbyshire 216-6, Worcestershire 421
In-form Matt Critchley has gone past 50 for the sixth time this season.
The young man from Chorley has now quickly raced on to 61, having been joined by Alex Hughes at the crease.
Image source, Getty Images