Moeen Ali hit a century for Worcestershire before the hosts collapsed from 215-3 to 287 all out on day one against Lancashire at New Road.
Left-hander Ali had made 104 by the time he was the seventh wicket to fall, becoming the second of Kyle Hogg's four victims when he was caught behind by wicketkeeper Gareth Cross.
Tom Fell weighed in with 43 during a fourth-wicket stand of 91 in 28 overs, only for his departure - run out by Lewis Reece's throw - to spark a rush of wickets.
Worcestershire made 38 in 13 overs before their opening pair were split up by seamer Tom Smith's third delivery which accounted for Daryl Mitchell, whose outside edge was snapped up in the slips by Andrea Agathangelou.
Opener Matt Pardoe and Moeen added 54 in 17 overs before the former was dismissed by left-arm medium-pacer Reece for 35 in the final over before lunch.
Thilan Samaraweera was stumped for six when he ambled out of his ground, but Moeen went on to reach three figures for the third time in the LV= County Championship this season.
He eventually fell during the first over with the second new ball, by which time Ross Whiteley, who marked his four-day debut for Worcestershire with a first-ball duck, and Joe Leach had already been dismissed cheaply.
Worcestershire at one stage lost lost six wickets for 37 runs in 15 overs before Alan Richardson (21) and Graeme Cessford (13 not out) produced an entertaining last-wicket stand worth 35.
Left to bat one over before stumps, Lancashire skipper Glen Chapple volunteered for nightwatchman duties and duly saw out a Richardson maiden.