Michael Yardy powered to an unbeaten century as Sussex ended day two of their LV= County Championship Division One match against Derbyshire 105 runs ahead with two wickets in hand at Derby.
Yardy finished the day on 121 from 192 balls, leading his side to 328-8 in response to the home team's opening effort of 223 all out.
Summer signing from Surrey, Chris Jordan, weighed in with 92 as the pair put on 179 for Sussex's sixth wicket, with the visitors struggling at 109-5 when the pair joined forces at the crease.
He and Yardy took it to the home attack, scoring freely with Yardy's ton coming off 151 balls, including 12 boundaries before Jordan was finally dismissed off the bowling of Tim Groenewald, with Ross Whiteley taking the catch to leave Sussex 288-6.
Australian bowler Steve Magoffin (9) was out to Mark Footitt, who then picked up his fifth wicket when bowling James Anyon for five before Monty Panesar survived 20 balls until the close to resume day three with Yardy.
Earlier, Derbyshire began the day on 158-6 but Ross Whiteley could not add to his overnight score of 12, caught by Joe Gatting off Jordan.
Jonathan Clare and Richard Johnson pushed the score past 200 before Clare was bowled by Anyon for 25, before the same bowler dismissed Groenewald the next ball.
Footitt was stumped by Ben Brown off Panesar for six, leaving Johnson unbeaten on 22 and the home side all out for 223.