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Kookaburra balls being used in this round of games plus first round in July
D1: Lancashire, put in by leaders Surrey, rally from 119-5 to be bowled out for 274
Teams who won the toss batting first in all the other games
D1: Essex duo Dan Lawrence and Tom Westley hit tons at home to Warwickshire
D1: Nick Gubbins & Liam Dawson going well for Hampshire against Middx
D1: Rob Keogh out for 97 for Northants against Kent in battle of bottom two
D1: Somerset bowled out for 163 at home to Nottinghamshire
D2: Alex Lees hits a ton as leaders Durham pile up a big score at Leicester
D2: Second-placed Sussex bowl out Glamorgan for 242
D2: Fin Bean makes a century for Yorkshire at home to Gloucestershire
D2: Pears opener Jake Libby still there but Pears four down at home to Derbyshire
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Northamptonshire 104-4 v Kent
The hosts lost their openers cheaply and they were in a bit of trouble when Luke Procter also fell cheaply to leave them 42-3.
But a partnership between Sam Whiteman (40) and Rob Keogh - not out on 40 - had put them back on track nicely before the former fell with the last ball before lunch.
Durham 150-1 v Leicestershire
Martin Emmerson
BBC Radio Newcastle at Leicester
Durham won the toss this morning and had 100 runs on the board in just over an hour.
Michael Jones and Alex Lees (66 at lunch) put together a stand of 145, which is Durham's highest opening partnership of the season. Jones was out just before lunch, clipping a ball from Ed Barnes to Colin Ackermann at short mid-wicket, when on 78.
It looks like a cracking batting track.
In the heat of Grace Road I would rather be batting today that toiling in the field.
Lancashire 98-3 (28 overs) Surrey
Quite a battle for Lancashire after being stuck in by Surrey.
The champions cashed in on the new Kookaburra ball to take three wickets inisde the first 20 overs, including the key one of captain Keaton Jennings.
But, since then, Dane Vilas (28) and Daryl Mitchell (22) have restored a bit of order with a half-century partnership, completed by Vilas off Sam Curran on the last ball before lunch.
Northamptonshire 104-4 v Kent
Fourth wicket down on the stroke of lunch!
Wes Agar has a second and new skipper Jack Leaning now has three catches in the slips today!
This time it's Sam Whiteman who goes for 40 from 74 balls.
He flashed at it and will be thinking over lunch that he wished he hadn't.
Yorkshire 139-3 v Gloucestershire
Yorkshire have fought back well from 33-2 after losing Adam Lyth and skipper Shan Masood cheaply.
They have been led by an unbeaten 65 from opener Fin Bean.
Hampshire 92-3 (30 overs) v Middlesex
Kevin Hand
BBC Radio London at the Ageas Bowl
An even morning in Southampton but one that Hampshire will be relieved to finish with only three wickets down.
All eyes were on how the Kookaburra ball fared and there was pace and bounce for Tom Helm early on while his skipper Toby Roland-Jones, of a similar height but down on pace in latter years, found some early swing.
It was the movement through the air that accounted for the first wicket when Fletcha Middleton fished at a wide offering from the former England seamer.
Joe Weatherly soon followed to Helm and when Josh Caires, in-form Stephen Eskinazi to bolster the spin options, picked up James Vince it threatened to be a tough morning for the hosts.
The pitch is particularly dry and with extreme heat is likely to play even more into the spinners' hands as the game wears on, which is why the decision to drop Mason Crane for the pace of James Fuller raised a few eyebrows.
Somerset 106-4 v Nottinghamshire
They lost the toss, but it’s been Nottinghamshire’s morning at Taunton.
Brett Hutton single-handedly reduced Somerset to 48-3 in a superb opening spell before Tom Abell and Tom Kohler-Cadmore rebuilt.
Matt Carter ended a promising fourth-wicket stand with just his seventh ball of the day to remove Abell and put Notts firmly in the driving seat on a good day for batting.
Lancashire 90-3 v Surrey -
It has been warm work and hard going for Lancashire at The Oval this morning.
But Dane Vilas and Daryl Mitchell have carried the attack back in the run-up to lunch, with a six each over the shorter boundary.
Northamptonshire 101-3 v Kent
Rob Keogh (38) and Sam Whiteman (39) have helped Northants to pass 100 just before lunch.
Leicestershire v Durham 145-1
Finally the Leicestershire bowlers have something to celebrate.
Colin Ackermann pouches the chance as Michael Jones falls to Ed Barnes for a rapid 70-ball 78 to end Durham's 145-run opening stand.
Scott Borthwick strides to the crease to negotiate the few minutes before lunch.
Essex 112-2 v Warwickshire
Essex have recovered well from the loss of those two early wickets.
Skipper Tom Westley has now gone past his half-century on 63, well supported by Surrey-bound Dan Lawrence on 37.
Somerset 100-4 v Nottinghamshire
James Rew strokes Lyndon James for back-to-back boundaries and the home side bring up three figures before lunch in the 27th over.
Some late morning blows after a tough morning.
Somerset 95-3 v Nottinghamshire
Tom Kohler-Cadmore with the shot of the morning as he launches Matt Carter into the top tier of the pavilion.
It's well fielded in the long room.
Glamorgan 68-4 (23 overs) v Sussex
Glamorgan have lost their fourth wicket at Sophia Gardens.
Opener Andrew Salter lasted almost an hour and a half and faced 60 balls for his 22. But he has gone now, bowled by South African Ari Karvelas
Worcestershire 85-1 Derbyshire
Derbyshire have taken the first Worcestershire wicket at New Road.
Gareth Roderick made 40 before being bowled by Ben Aitchison.
Jake Libby is on 35 not out as lunch approaches.
Hampshire 76-3 v Middlesex
Big wicket for Middlesex and a major blow for Hampshire!
James Vince had been batting so well and on this pitch in these conditions he would have planned to go on to a big score.
But Josh de Caires - who Vince sent for six twice - has his revenge as he traps him lbw as he tries to flick the ball away off the pads.
There's some debate in the BBC commentary team about that call from the umpire. Did it pitch in-line and was it going on to hit the stumps?
Somerset 88-4 v Nottinghamshire
The oil spill strikes!
Matt Carter lands the ball in the suspect patch with the first ball of his second over and it skids on to Tom Abell.
The ball catches his outside edge and heads straight into the hands of Steven Mullaney at first slip.
Another blow for Somerset.
Somerset 88-3 v Nottinghamshire
Somerset are recovering well through Tom Abell and Tom Kohler-Cadmore who have put on 40 after a slippery start.
But on the subject of slippery, the talk at Taunton is of an unfortunate oil spill dispatched on the wicket from a leaky roller.
The patch is on a good length for right-arm spinner Matt Carter who comes into the Notts attack.
Can he take advantage?
Lancashire 47-3 v Surrey
The acid test of any Kookaburra ball ia apparently how it behaves in the first 20 overs.
Surrey were the only side to insert the opposition today - and they have been rewarded three times in those 20 overs.
Clearly their morning so far - and that of the Kookaburra too, with wickets tumbling everywhere, except unhappy Leicester.
Yorkshire 116-3 v Gloucestershire
Another classy knock from the latest young gun off the Yorkshire batting production line.
Finlay Bean brings up his second first-class fifty off just 59 balls including eight fours and a maximum.
The opener has helped Yorkshire rebuild and shared a 57-run third-wicket stand until Dawid Malan was caught behind off a lazy stroke to Ben Charlesworth for 28.
The hosts went on to bring up three figures in the 19th over - an even morning at Headingley.