Gloucestershire's Will Tavare, nephew of former England batsman Chris, scored an unbeaten century on his County Championship debut to help the hosts reach 292-5 in the Division Two clash with Hampshire at Bristol.
Tavare marked his debut appearance in style with an unbeaten 135, ably assisted in a key second-wicket partnership by captain Michael Klinger, who scored 81 runs off 168 balls before being caught behind off Hampshire's new South African signing, Kyle Abbott.
The fall of Klinger's wicket preceded the departures of Abbott's second victim Alex Gidman (nought), and Hamish Marshall (four) and James Tomlinson then dismissed Chris Dent for six in the morning - his 300th first-class wicket for Hampshire - and he removed New Zealander Marshall in the first over following tea.
Will Gidman appeared late in the day to steady the innings and put 55 more runs on the board before perishing to Sean Ervine.
At Chelmsford, Derbyshire paceman Tim Groenewald took a hat-trick and the prized wicket of England captain Alastair Cook as Essex were bowled out for 94 on day one.
Cook was comfortably Essex's top scorer with 35 runs of an innings that saw four colleagues fall for ducks. Derbyshire bowlers Mark Footitt and Groenewald did all the damage with the ball, returning respective figures of 5-29 and 5-44.
England all-rounder Ravi Bopara lasted just 15 balls for three runs and headed back to the pavilion in the 20th over after he was caught by Wes Durston off Groenewald, becoming the first victim of the hat-trick.
Groenewald bowled Greg Smith with his next ball and then had Ben Foakes snared lbw as the 30-year-old South African completed his feat.
James Foster (13), England spinner Monty Panesar (14) and Tymal Mills (12 not out) made it to double figures for the home side in a dismal innings.
In reply, Derbyshire opened up a 45-run lead by posting 139-5 with West Indies lynchpin Shivnarine Chanderpaul, who reached 66 not out, and Richard Johnson taking the visiting team to the close.
Elsewhere, New Road saw 12 wickets fall on day one as Worcestershire were dismissed for 224 in their Division Two match against Kent.
The Pears began their season with a rain-affected draw against Hampshire and were bowled out for a below-par total in their home opener, with Alexei Kervezee the only man to get past 50.
But they dismissed Kent openers Sam Northeast and Rob Key after tea to leave the visitors on 39-2 in reply at the close of play.