Paris (AFP) - Castres boosted their chances of progressing to the Top 14 play-offs with a 33-28 victory at Grenoble on Friday.
Castres followed up last week's 15-9 win over Toulouse with this success which lifted them up a place into the crucial sixth spot on 53 points.
Grenoble, aiming for a third consecutive win in the championship, remained in eighth spot on 47 points.
Thomas Combezou opened the scoring with an 18th minute try for Castres, who looked menacing on each incursion into Grenoble territory.
On one of these Alex Tulou was awarded a try despite Grenoble protests at a suspect pass from Julien Caminati.
Grenoble, who were being made to suffer in the scrum, were kept afloat by Jonathan Wisniewski's accurate penalty kicking - he was to convert seven in total.
But Castres crossed for a third time through David Smith in the 70th minute, with Grenoble's one and only touchdown three minutes from time from Maritino Nemani earning them an attacking bonus point.
The visitors meanwhile also had the boot of Benjamin Urdapilleta to thank for the win, the Argentine fly-half firing over three conversions and four penalties.
Castres coach Christophe Urios said: "We've been doing interesting things, sometimes brilliant, sometimes laboured, in our last few away games.
"I reckon over the entire game we deserved this result. We're happy with the win, it's an important one for the end of the championship."
Grenoble second row Mathias Marie said: "We fought to come back into the game in the closing stages but we lacked concentration.
"We were missing accuracy throughout."
Leaders Clermont host rock-bottom Agen feeling confident enough to rest scrum-half Morgan Parra, who took a knock to the head two weeks ago against Toulon.