Stuart Broad and James Anderson on opposite sides as Notts bowl out Lancashire for 214.
Surrey's Gus Atkinson takes 6-68 - his first five-for - for 2022 champions against Essex.
Second-placed Hampshire all out for 229 on day one against Warwickshire.
Australia batter Steve Smith makes debut for Sussex at New Road
Jonny Bairstow takes three catches behind stumps for Yorkshire against Glamorgan.
On-loan paceman Henry Brookes takes 6-20 on debut for Derbyshire.
Essex 186-3 v Surrey
That is a very big blow.
Matt Critchley hits a second six in successive Cameron Steel overs and advances to 47 not out.
Image source, Rex FeaturesQuote MessageI think that may well have gone into the river - he got a lot of that."
BBC Radio London's Mark Church
Yorkshire v Glamorgan 161-6
Jordan Thompson inflicts further damage on Glamorgan, as Chris Cooke finds Matt Fisher at mid-wicket.
Hampshire 166-7 v Warwickshire
James Vince and James Fuller have added 33 in just over five overs, although the ball is still hooping around despite being 51 overs old.
It all suggests the track is good but the conditions are aiding the Bears attack.
Fuller has four fours in his 20. Vince is on 41 from 63.
Essex 177-3 v Surrey
Cameron Steel continues and Matt Critchley fetches the ball from outside off stump and clears the rope at mid-wicket. He progresses into the 40s and is close to overtaking partner Tom Westley.
Which of them will get to 50 first?
Notts 0-0 v Lancashire 214
James Anderson has the ball in his hand and will be up against openers of England present and England's not-so-distant past.
Ben Duckett is alongside Haseeb Hameed as Notts begin their reply to Lancashire's 214 all out.
Worcs 231-7 v Sussex
Matthew Waite reaches 50 for the second time for Worcestershire this season from just 40 balls as he pushes Fynn Hudson-Prentice for a single. Good counter-attacking knock so far.
Derbys 32-0 v Leics 120
Having made 7, 0 and 1 in his first three innings for Derbyshire, Pakistan's Haider Ali is due a score.
Leicestershire will be very much hoping that it doesn't happen today but he already has three fours, the latest pulled away with authority from the bowling of Chris Wright. He is 21 not out.
Yorkshire v Glamorgan 154-5
Image source, Rex FeaturesYorkshire get the big wicket of Marnus Labuschagne, who edges behind off George Hill for a patient 65.
A third catch of the innings for Jonny Bairstow.
Essex 156-3 v Surrey
Matt Critchley puts Gus Atkinson away for four and that brings up a 50 partnership with skipper Tom Westley. Critchley is 25 not out and Surrey call up Cameron Steel to bowl some leg-spin.
Notts v Lancs 214
Lancashire all out at Trent Bridge.
James Anderson gets a leading edge off Olly Stone and Ben Duckett takes the catch, leaving Tom Bailey stranded on 48 not out off 29 balls.
Brett Hutton was the star with 5-66.
Image source, Getty ImagesWorcs 223-7 v Sussex
Having been 44-5 during the morning session, Worcestershire are now closing in on a batting point at New Road.
Joe Leach lifts a leg-stump half-volley from Fynn Hudson-Prentice over square leg for six and is 27 not out.
Matthew Waite has 44 off 33 balls at the other end and together they have so far added 63 for the eighth wicket.
Somerset v Northamptonshire 137-4
Anthony Gibson
BBC Radio Somerset
Rain and bad light at Taunton, although the umpires kept the players out there long enough for Somerset to pick up three badly-needed post-lunch wickets - Whiteman, Vasconcelos and Saif Zaib.
The skies are brighter to the south, where the weather is coming from, but further showers are forecast.
Hants 141-7 v Warwicks
Kevan James
BBC Radio Solent commentator
Having been at one stage 83-1 before lunch, things look a little different now for Hampshire.
The Warwickshire seam attack have, to a man, bowled a little tighter since the break and it has brought rewards.
Fletcha Middleton's innings of 49, though, again showed much promise but he inevitably succumbed to an edge off the impressive Chris Woakes.
Essex 150-3 v Surrey
Tom Westley is still there but only just - bringing his bat down at the last second to keep out two magnificent, rapid yorkers by Kemar Roach. It's a maiden and Westley remains 37 not out.
Notts v Lancs 206-9
Tom Bailey is teeing off against Olly Stone with only one wicket remaining and manages to hit a six over the wicketkeeper's head.
The ball has landed and been lost somewhere in the covers and we now have several Notts fielders trying to locate it.
In the meantime, umpire Martin Saggers grabs another of a similar condition from his trusty case and we're ready to get going again.
Derbys 7-0 v Leics 122
Derbyshire have begun their first innings and Harry Came has square cut the first boundary off Chris Wright. Can Leicestershire redeem themselves with the ball after being bowled out cheaply in 39.5 overs?
Hampshire 137-7 v Warwickshire
Chris Woakes bangs in a short one, Ian Holland ducks and hooks the ball away in the same movement, skying it to Danny Briggs who stood patiently just inside the rope at fine leg and waited for his meat and drink to be delivered.
Holland puts his hand on his head. He didn't need to do that. James Fuller is next in to join James Vince and slaps Woakes for a four from his third ball. He's going to need a new bat.
Hampshire just 54-6 since the ball before lunch.
Yorkshire v Glamorgan 137-4
Matthew Henry
BBC Sport at Headingley
Image source, Rex FeaturesJonny Bairstow had been having an quietly efficient day behind the stumps but that was a stunning catch.
He was wrong-footed by an inside edge from Kiran Carlson but dived low to his left to take the ball one-handed.
He seemed to enjoy it too, giving a big celebration towards the crowd.
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From Andy: "Darn. Was just feeling smug about my astute selection of Henry Brookes in my fantasy XI this week, when I realised that I picked Jack Brooks by mistake, who isn't even playing. #bbccricket, external"
Essex 149-3 v Surrey
It's a few years since Tom Westley played for England but you can't bowl that line to him and expect to get away with it.
The Essex skipper clips Gus Atkinson away for four and is now 37 not out, with Matt Critchley on 20. Their stand is currently worth 45.