Leading pair Somerset and Essex hold the upper hand after day one of their respective Specsavers County Championship games against Hampshire and Nottinghamshire.
James Hildreth led the way with an aggressive 105 from 129 balls as leaders Somerset piled up 408 at Taunton.
He was backed up by captain Tom Abell (82), Tom Banton (79) and George Bartlett (68) before Kyle Abbott ripped out the lower order for figures of six for 84. Jamie Overton removed Oliver Soames in the second over of Hampshire's reply as they closed on 15 for one.
Essex, meanwhile, bowled out Nottinghamshire for 213 after the hosts had chosen to bat first. Jamie Porter, Peter Siddle and Aaron Beard took three wickets apiece, with Steven Mullaney's 74 the only score of note.
Essex reached 72 for one in reply despite losing Sir Alastair Cook for just two.
Sean Dickson was 146 not out as Kent finished the opening day on 338 for two against Warwickshire at Canterbury. Dickson put on 132 with opening partner Zak Crawley and an unbroken 152 with Daniel Bell-Drummond, who will resume on 68.
At Scarborough, Yorkshire opener Will Fraine scored his maiden first-class century as his side made 327 against Surrey despite a middle-order collapse.
Fraine (106) and Adam Lyth (55) shared an opening stand of 116 but the Tykes slipped from 201 for two to 250 for eight, before captain Steven Patterson led a tail-end wag with 46. Surrey closed on 48 without loss in reply.
Division Two leaders Glamorgan were 354 for six against Worcestershire thanks to a partnership of 138 between Marnus Labuschagne (106) and David Lloyd, who fell three short of a century.
Opener Nick Selman had earlier made 67 while Brett D'Oliveira took four for 63.
Lancashire recovered from 81 for three to reach 275 for five against Durham.
Rob Jones (52) put on 60 with Liam Livingstone (35) and then 87 with captain Dane Vilas, who will resume on 67 not out.
Billy Godleman scored a century but Fynn Hudson-Prentice fell agonisingly short as Derbyshire dominated the opening day against Middlesex.
Hudson-Prentice was out for 99 from 133 balls on his first-class debut for Derbyshire and Luis Reece fell for 96, but the home side closed in a strong position on 372 for four with Leus du Plooy 50 not out.
Northamptonshire held the upper hand over Sussex at Hove as Saif Zaib led a lower-order rally after Ollie Robinson's six for 63.
Zaib came to the wicket at 99 for six but shared in partnerships of 51 and 54 with Adam Rossington and Brett Hutton before Nathan Buck (34no) and Ben Sanderson (28) put on 68 for the last wicket to steer Northants to 273.
Sanderson and Hutton took early wickets to leave Sussex seven for two from seven overs in reply.