Jack Shantry took six wickets as Worcestershire forced Surrey to follow-on and closed in on victory at the Kia Oval.
Shantry's emphatic display included four wickets in 11 balls as he took his total haul in the LV= County Championship Division Two clash to seven wickets.
After rain meant there was no play before lunch, Zafar Ansari's unbeaten 77 was the only positive for the hosts as the Worcestershire attack restricted them to 206 all out and a big deficit of 270.
Ansari added a further unbeaten half-century for the hosts, who were asked to follow-on, but at 111-3 at the close, trailing by 159 runs, theirs looks an onerous task.
At the Ageas Bowl, captain Jimmy Adams hit his second half-century of the match as Hampshire looked to close out their LV= County Championship Division Two clash against bottom side Derbyshire.
Having scored 60 on day one, Adams made 67 to help the Division Two leaders reach 214 for five declared, setting Derbyshire a testing 346-run victory chase.
They had, at least, managed to get to the close without loss of a wicket, with Stephen Moore on 22 and Paul Borrington not out on nine.
Earlier, Danny Briggs put in a superb stint of 5-50 to wrap up Derbyshire's first innings for 257.
Will Bragg helped edge Glamorgan into a 152-run lead over Essex on a rain-hit third day at Chelmsford, where home bowler Reece Topley claimed his 10th wicket of the match.
Bragg, who had scored 93 in the first innings, fell just short of a second half-century when he was caught on 46 by New Zealander Jesse Ryder in the slips, with the visitors looking to post a commanding advantage.
South African Jacques Rudolph equalled Bragg's 46, but Topley and Thomas Moore (3-62) would not let Glamorgan settle. With just a 152-run overnight lead they need sizeable partnerships from their last two wickets if they are to avoid defeat.
Leicestershire will resume their second innings on day three on 12 without loss, a lead of 21, after what has proved to be an even contest to date against Gloucestershire.
In response to the home side's 269 on day one, Gloucestershire lost wickets at regular intervals until a 107-run partnership for the fifth wicket, inspired by a knock of 93 from former-England wicketkeeper Geraint Jones.
Will Gidman also added an unbeaten 52, but ran out of partners as the visitors were all out for 260, with Nathan Buck's 4-81 doing most of the damage. The contest is nicely poised at the half way stage.