Kyle Coetzer and David Sales struck centuries as Northamptonshire's batsmen dominated the second day of their LV= County Championship Division Two clash with Gloucestershire at Wantage Road.
Scotland international Coetzer was the first to reach his milestone as he made 122 off 230 balls to help promotion-chasing Northants close on an imposing 369 for three.
Sales put some previous patchy form behind him as he hammered an unbeaten 126 from 137 deliveries, while captain Stephen Peters also contributed 87 off 153 balls.
Northants began the day on 13 without loss, 345 runs behind their opponents, with Peters resuming on 12 and Coetzer on one.
Peters, who is playing in his first championship match since returning from a broken finger, was to go on to complete a half-century off 78 balls.
That came as part of a mammoth opening partnership with Coetzer as Gloucestershire's attack struggled to get much out of a placid wicket.
The hosts resumed after lunch on 112 without loss, Coetzer soon reaching 50 off 116 deliveries as his side picked up where they left off.
In the end it came down to 18-year-old first-class debutant Tom Shrewsbury to finally break the stand on 170 when he forced Peters to edge to wicketkeeper Gareth Roderick.
But any hopes the visitors had of that breakthrough bringing a change of fortunes were dashed as Sales piled on 135 alongside Coetzer for Northants' second wicket.
Coetzer completed his eighth century in first-class cricket and third in all competitions this season off 202 balls with a straight four off James Fuller - the final delivery before tea.
Veteran Sales raced to his first half-century of the campaign off 67 balls early in the evening session.
Having batted so well, Coetzer departed tamely in the final over before the second new ball was due when he chipped Benny Howell to Chris Dent at midwicket.
But there was no stopping Sales completing an explosive century - his 27th first-class ton - off just 107 deliveries with a crunching four through midwicket off Fuller.
Alex Wakely then became the first batsman to miss out on a big score as he edged Fuller behind with five overs of the day left.
Australia international Cameron White survived until the close along with Sales and will resume tomorrow on six not out with the hosts looking for a huge total.