Alexei Kervezee's 110 and 99 from Moeen Ali strengthened Worcestershire’s position at stumps on day three of their LV= County Championship clash with Derbyshire at New Road.
Former Netherlands international Kervezee reached his ton off 132 balls and helped the hosts, responding to Derbyshire's first-innings 219, reach a hefty 432 for nine at the close.
Worcestershire therefore held a lead of 213 with a day left to push for victory.
Resuming on 31 without loss, openers Daryl Mitchell and Matthew Pardoe put on 72 before the Derbyshire attack had belated success when Mitchell was caught by Dan Hodgson off David Wainwright for 26.
On a frustrating day in the field, spinner Wainwright was the pick of the Derbyshire attack as he finished with 3-102 off his 28 overs.
Wainwright removed Pardoe one run short of a half-century, and the visitors scented a change in fortune when Tom Kohler-Cadmore was trapped lbw to Tony Palladino for 11.
Andrew launches one into the Premier Inn and has to get a new bat #Blastpractice
— Worcestershire CCC (@WorcsCCC) April 29, 2014
But those hopes were extinguished by a fine fourth-wicket stand of 78 between Moeen and Kervezee.
Moeen fell agonisingly short of a century when he met Wes Durston with a back-foot drive that Tim Groenewald held just before tea.
Kervezee battled on to make his century before he was caught by Wayne Madsen off Mark Footitt to leave Worcestershire on 388 for seven.
Jack Shantry's departure from the next ball left Footitt on a hat-trick, but Footitt would have to wait two more overs for his third wicket of the innings when he had Saeed Ajmal caught by Chesney Hughes on one.
At the close, Gareth Andrew has briskly moved to an unbeaten 71 from 54 balls - including five sixes - with last man Charles Morris 13 not out.