Gloucestershire and Middlesex strengthened their push for promotion, while Northamptonshire's hold on first place was narrowed after they could only draw against Derbyshire.
Leaders Northamptonshire have 154 points after a drawn match against Derbyshire at the County Ground and are now 18 points ahead of second place.
Derbyshire found themselves 39-5 batting first, but Ross Whiteley's 103, Jonathan Clare's 82 and Tony Palladino's 60 lifted them to 364. Chaminda Vaas claimed 4-105.
Rob Newton's 94 was invaluable as the home side replied with 275. Mark Turner snared 5-32 and Tim Groenewald 3-60.
Derbyshire reached 268-4 declared second time around, with Wes Durston (62) top-scoring. Lee Daggett claimed 2-60 for the home side.
Chasing 358, Northamptonshire slipped to 126-5 but Andrew Hall (66 not out) and Niall O'Brien (37 not out) ensured they reached 229-5 before a draw was agreed.
Derbyshire are fourth on 118 points with three wins, four draws and three defeats with a chance of promotion.
Middlesex are second on 136 points and have a game in hand on all the teams around them, after a six-wicket victory against Surrey in Guilford.
Middlesex slipped to 51-4 batting first, but Jamie Dalrymple's 122 not out took them to 308. Tim Linley claimed 3-60.
Surrey collapsed from 107-5 to 117, including four ducks, as Tim Murtagh took 5-30 and Corey Collymore 4-28.
Following on, Tom Maynard smashed 141 from 101 balls, Zander de Bruyn made 82 and Rory Hamilton-Brown 62 as the home side scored 379 at 5.35 runs per over.
Tim Murtagh was pick of the bowlers with 5-98 while England hopeful Steven Finn returned 2-79.
Chasing 189 for victory, Middlesex wobbled to 84-3, but Sam Robson's 94 not out guided them home to win by six wickets.
Surrey are fifth on 111 points, with three wins, four draws and three defeats and can still claim promotion.
Gloucestershire are third on 134 points after a innings and 142-run thrashing of Kent in Cheltenham.
Kent managed 205 first time around as Darren Stevens made 67, and James Tredwell hit 45. Will Gidman picked up 5-38.
Gloucestershire piled on 515 in their first innings, Chris Taylor making 196 and Alex Gidman 79. David Balcombe's 5-103 the pick of the away side's bowlers.
Kent crumbled to 168 in their second innings, Simon Cook hitting 46 not out from 39 balls, but David Payne's 4-60 and Jon Lewis's 3-31 secured the innings and 142-run victory for Gloucestershire.
Kent are eighth on just 78 points, with two wins, one draw and seven defeats..
The next round of fixtures sees seventh placed Glamorgan host Northamptonshire, Gloucestershire face Surrey and sixth placed Essex against bottom side Leicestershire from July 27. Middlesex play Derbyshire from July 29.