Worcestershire gained a narrow lead over Yorkshire before losing early second innings wickets on the third day of the LV = County Championship clash with the champions at New Road.
Paceman Gareth Andrew completed a five wicket haul when Tim Bresnan was caught at third slip for a fine 83.
Yorkshire were dismissed for 307 – four runs adrift of Worcestershire's first innings total of 311 – after resuming on 298-9.
Ryan Sidebottom required a runner after suffering a calf injury yesterday and he finished unbeaten on 14.
Andrew finished with figures of 5-85 and Jack Shantry (4-65) were the main wicket-takers.
Jack Brooks, who had returned 5-56, in Worcestershire's first innings, again did most of the early damage.
But it was Bresnan, taking the new ball in place of the injured Sidebottom, who trapped Richard Oliver lbw for one after he had offered no shot.
Moeen Ali got off the mark in impressive fashion with a cover drive for four off the former England paceman.
But it was his only scoring shot before he edged a fine delivery from Brooks to Jack Leaning at second slip.
A lifting delivery from Brooks was nicked by Worcestershire skipper Daryl Mitchell (8) to Alex Lees at first slip.
Alex Gidman (4) was caught behind by Andrew Hodd off Brooks with the total 21-4.
First innings century-maker Tom Fell and Tom Kohler-Cadmore dug in to add 27 in 14 overs.
Fell turned Bresnan off his legs for four and Kohler-Cadmore drove Will Rhodes to the boundary as well as thick edging the same bowler to the ropes.
Steve Patterson picked up two wickets in two balls with Fell (14) caught at first slip by Lees and Ben Cox (0) adjudged lbw.
At lunch-time Kohler-Cadmore was unbeaten on 15 and Andrew nought not out out of 55-6.