Gloucestershire on top after 17 wickets
Gloucestershire had the better of a wicket-laden opening day with Northamptonshire, who were 73 for seven in reply to 220 by stumps at Bristol.
Luke Evans took four and Andrew Hall three for Northants, but fifties from Alex Gidman and Jonathan Batty helped LV= County Championship Division Two’s bottom team to a serviceable total.
James Fuller and Ian Norwell then shared six wickets to leave the visitors in deep trouble.
Pitch inspector David Hughes found no fault with the pitch on a day dominated by the seam bowlers and featuring some pretty ordinary batting.
It was Hall who ripped out the home side's top order after winning the toss, taking his wickets in the space of 11 balls at a cost of two runs as Gloucestershire slumped from 41 without loss to 44 for four.
However, Gloucestershire’s total was soon looking more than decent as Northants plunged from 30 without loss to 72 for seven.
Only Stephen Peters, with 35, offered much resistance as Fuller sent back Niall O'Brien, Rob Newton and Hall with a pacy spell from the Pavilion End.
Norwell was just as impressive from the Ashley Down Road End, claiming the wickets of David Sales, Kyle Coetzer and Peters.
There was little sign of carnage ahead when Gloucestershire openers Benny Howell and Ed Cowan put together a solid opening stand of 41 at the start of the day.
Then Howell, on 29, was dropped at second slip by Peters off Evans and it signalled a transformation in fortunes. Next ball Evans rapped Howell on the pads and gained an lbw verdict.
Cowan, back in Gloucestershire's team after a short spell as temporary overseas player earlier in the season, went leg-before for eight in the next over as Hall began to make rapid inroads, swinging the delivery and getting some seam movement from the Ashley Down Road End.
His next two overs saw Dan Housego’s off stump knocked out of the ground and Hamish Marshall pinned lbw on the back foot for a duck.
Gidman launched a counter-attack with four fours in an over from David Willey, all punched through the off side. But Ian Cockbain had his middle stump sent flying by Willey.
It was 95 for five at lunch and the afternoon session saw Gidman reach his half-century off 48 balls, with 10 fours. He added 33 for the sixth wicket with brother Will before falling to another lbw verdict, Willey claiming his second victim.
Will Gidman was caught in the slips, driving at a wide ball from Jack Brooks, and when Fuller edged a catch to the wicketkeeper off Evans Gloucestershire were 151 for eight.
Batty and Anthony Ireland, on loan from Middlesex, saw the home side to tea at 206 for eight and the former Surrey keeper reached a battling half-century straight after the interval, having faced 89 balls and hit six fours.
Ireland soon perished to a catch behind off Evans for a handy 22 before Batty was last man out, caught at point making room to hit Evans - who took 4-38 - through the off side.