Eight fixtures in Round Five of the season
Essex, Hants & Sussex all bowled out before tea
Durham & Derbyshire only two counties not playing in this round
James Anderson plays first game of season for Lancashire
And that's where we'll also bring our coverage to a close for today.
Thanks for being with us. Just a reminder you can read full close of play reports right here on the BBC Sport website and app.
We'll be back with the second day's play from 10:45 BST on Friday.
Group 1:
Trent Bridge: Nottinghamshire 188-4 v Essex 99 - Nottinghamshire won toss and elected to bowl first
Edgbaston: Warwickshire 271-7 v Worcestershire - Worcestershire won toss and elected to bowl first
Group 2:
Ageas Bowl: Hampshire 79 v Somerset 142-2 - Somerset won toss and elected to bowl first
Grace Road: Leicestershire 306-6 v Surrey - Leicestershire won toss and elected to bat first
Lord's: Middlesex 210 v Gloucestershire 19-1 - Gloucestershire won toss and elected to bowl first
Group 3:
Old Trafford: Lancashire v Glamorgan 117-3 - Glamorgan won toss and elected to bat first
Northampton: Northamptonshire 214-5 v Sussex 106 - Northants won toss and elected to bowl first
Headingley: Yorkshire v Kent 224-7 - Yorkshire won toss and elected to bowl first
And you can see the full scorecards from all those matches on this page.
And that is stumps in all of our eight fixtures.
Stay there and we'll show you how things finished before we head off for the day....
Hampshire 79 v Somerset 142-5
Stumps at the Ageas Bowl too.
Hampshire miss out on finishing the day with a sixth wicket as nightwatchman Jack Leach is put down at third slip off Keith Barker.
Tom Abell finishes not out on 52 at the other end. Somerset will resume tomorrow with a lead of 63.
Nottinghamshire 188-4 v Essex 99
Got very gloomy all of a sudden and the players are heading off with a couple of overs still to bowl. That will probably be stumps too.
Notts head off on 188-4 which is a lead of 89.
Steven Mullaney (63 not out) and Lyndon James (42 not out) have put on 105 for the fifth wicket so far to capitalise on Luke Fletcher's bowling heroics earlier in the day.
Middlesex 210 v Gloucs 19-1
Gloucestershire see out the remaining couple of overs without any further damage and that's stumps.
What an exciting opening day at Lord's that was. The game is pretty finely balanced thanks to that late Chris Dent run out.
Goldsworthy b Holland 24 (Hampshire 79 v Somerset 137-5)
Hampshire with a welcome wicket out of nowhere towards the end of the day.
Lewis Goldsworthy's gritty knock comes to an end as he inside-edges Ian Holland on to his stumps.
A dogged 24 off 62 balls alongside Tom Abell.
Hampshire 79 v Somerset 137-4
A real captain's knock this one so far from Somerset's Tom Abell.
He reaches a very hard-earned half-century off 115 balls with his sixth four as he cuts Keith Barker to the point boundary.
Somerset now 58 runs ahead as we move towards stumps.
Dent run out 10 (Middlesex 210 v Gloucs 13-1)
What on earth has happened here?!
Chris Dent taps into the leg side, calls Kraigg Brathwaite through for a single but the West Indies Test captain isn't going anywhere.
Dent tries to get back but is run out.
Not ideal with a couple of overs left in the day.
Nottinghamshire 174-4 v Essex 99
Back-to-back boundaries for Steven Mullaney sees him bring up his half-century off just 57 balls.
He's struck 10 fours as well which just shows you how destructive he's been.
Notts now 75 ahead.
Nottinghamshire 166-4 v Essex 99
It's a run-fest all of a sudden at Trent Bridge.
Nottinghamshire are cashing-in here towards the end of the day as Lyndon James (40 not out) and Steven Mullaney (43 not out) find the boundary regularly.
Their partnership now worth 83 and their overall lead 67.
Six overs still to bowl this evening.
Middlesex 210 v Gloucs 0-0
Kraigg Brathwaite and Chris Dent get Gloucestershire's first innings started at Lord's.
Seven overs to survive until the close.
Northants 184-5 v Sussex 106
Northants batsman Saif Zaib goes to a fifth first-class half-century and what an important one it's been for his side.
They lead Sussex by 78 and that could grow significantly if Zaib sticks around until stumps. 10 overs to go.
Warwickshire 271-7 v Worcestershire
Stumps in Birmingham.
An evenly-balanced day finishes with Warwickshire on 271-7.
Worcestershire kept on plugging away despite Rob Yates' impressive 104 at the top of the order.
Josh Tongue bowled Olly Stone for a duck for the seventh wicket of the day.
Middlesex 210 v Gloucestershire
Gloucestershire left-arm paceman David Payne finishes the Middlesex first innings with two wickets in three balls to claim 5-31.
First Thilan Walallawita prods him to slip and then he cleans up last man Tim Murtagh.
Robbie White is left stranded on 72.
Leicestershire 306-6 v Surrey
Covers are on at Leicester with only three overs to bowl in the day.
Leicestershire have lost a couple more wickets in the evening session to be 306-6.
Lewis Hill (18) and Ed Barnes (1) both went shortly after the Foxes past 300.
Nottinghamshire 137-4 v Essex 99
Nottinghamshire starting to take command now.
Lyndon James (31 not out) and Steven Mullaney (23 not out) begin to open their shoulders and find the boundaries to bring up a 50 partnership for the fifth wicket.
Notts now with a lead worth 38.
Hampshire 79 v Somerset 101-4
Tom Abell (38 not out) and Lewis Goldsworthy (3 not out) have been digging in and scrapping it out for Somerset as they continue to build a lead.
Goldsworthy has been in for 29 balls so far and survived a fair few appeals from Hampshire.
Skipper Abell now comfortably the highest-scoring batsman of the day.
Yorkshire v Kent 224-7
And that's the close in Leeds.
Zak Crawley hit 90 for Kent before Yorkshire's bowlers fought back late in the day.
Middlesex 200-8 v Gloucs
Middlesex bring up their 200 at Lord's for a first batting bonus point but they've lost a couple more wickets in the process.
James Harris and Ethan Bamber have both fallen, but Robbie White is still there on 70.
He may run out of partners before he can get to a maiden first-class century and surpass his best of 99.