Racing Métro ran three unanswered tries past Top 14 leaders Toulouse on Saturday to close the gap at the top of the standings to a single point.
Racing ruled the roost in a one-sided affair at the Stade de France to grab a bonus point and underline their title credentials.
Biarritz cruised past Bayonne in the Basque derby in Spain after relegation-threatened Agen provided the shock of Round 22 by beating champions Clermont.
Perpignan secured a vital bonus-point win on the road in La Rochelle to stay firmly in the hunt for the play-offs while Brive ran riot at home to Bourgoin, scoring 50 points.
Friday: Castres 18-12 Toulon
Agen 26-17 Clermont
La Rochelle 16-34 Perpignan
Brive 50-6 Bourgoin
Biarritz 40-10 Bayonnais
Racing Métro 43-21 Toulouse
Sunday, March 26
Montpellier v Stade Français
SU Agen 26-17ASM Clermont Auvergne
Stade Armandie, Agen
Agen took a massive step towards safety with the biggest win of their season as Clermont, once again, failed to produce the goods away from home. The champions were simply outmuscled by a side who wanted it more.
Clermont got off to the perfect start when scrum-half Morgan Parra touched down after just three minutes. The rest of the first half would belong to the hosts however.
Agen leveled the scored when loose forward Jean Monribot sprinted home from almost half way. Pierre Bernard nailed a penalty before Tongan number eight Opeti Fonua extended the lead with another try on the counter attack to give Agen a 20-10 lead at the break.
Clermont pulled try back through George Pisi in the second half, but two more penalties for Bernard were enough to hand Agen victory.
Stade Rochelais Atlantique 16-34 USA Perpignan
Stade Marcel Deflandre, La Rochelle
Perpignan climbed into the top half of the table for the first time in months as they continued their winning streak.
With Agen and Brive winning this weekend, La Rochelle drop back into the relegation zone, four points short of safety.
It was all Perpignan in the first half as the visitors ran in four answered tries, with centre Rudi Coetzee (2) , wing Julien Candelon and hooker Guilhem Guirado all crossing the whitewash to give the Catalans a 29-9 lead at the break.
The second half was a much closer affair but USAP managed a fifth try when Jerome Porical off- loaded wing Andrien Planté, who scored in the corner.
Number eight Thomas Soucaze scored a late consolation try for the hosts
CA Brive Corrèze v CS Bourgoin-Jallieu
Stade Amédée Domenech, Brive
Brive climbed out of the relegation zone with a morale-boosting win, scoring seven unanswered tries in the process.
Brive led 17-3 at break thanks to tries from centre Fabrice Estebanez and full-back Julien Caminati
It was one-way traffic in the second period as wing Guillaume Namy, lock Retief Uys, scrum-half Agustin Figuerola and full-back Alexis Palisson all scored while Caminati added his second.
Biarritz Olympique 40-10 Aviron Bayonnais
Estadio Anoeta, San Sébastien (Spain)
A dominant bonus-point win sees Biarritz climb into third place in the standings while Bayonne have a massive task on their hands if they are to make the play-offs.
Biarritz out-scored their Basque neighbours four tries to one in a high-paced game - perfect preparation for their upcoming Heineken Cup quarter-final.
BO raced into a 14-0 lead inside the first ten minutes thanks to tries from wing Marcello Bosch and fly-half Julien Peyrelongue.
Kiwi lock Ross Filipo pulled a try back for Bayonne, but a drop from Damien Traille and touch-downs from Imanol Harinordoquy and Takudzwa Ngwenya gave BO led a 32-10 lead at half time.
Biarritz controlled the match in the second half, keeping Bayonne off the score board and adding two penalties via Dimitri Yachvili.
Racing-Métro 43-21 Stade Toulousain
Stade de France, Saint-Denis (Paris)
What a disappointment for Toulouse fans! Guy Novès' team certainly did not look like the defending European champions - despite having a full strength side - as they could only muster seven penalties, slotted by scrum-half Fred Michalak, in answer to Racing's three tries.
Racing dominated almost every sector in an impressive display. Les Franciliens are now just one-point off the championship lead.
The hosts led 13-3 after ten minutes following Jonny Leo's opening try, set up by Nicolas Durand. Racing fly-half Jonathan Wisniewski hit kept the scoreboard ticking until the break.
Racing took a 22-12 lead into the changing rooms but wing Julien Saubade extended their advantage soon after the restart.
Sebastien Chabal came off the bench in the last quarter and score within minutes of joining the fray while Wisniewski added his second drop gaol and a couple of penalties to ensure Toulouse did not get a losing bonus point.
Montpellier HR v Stade Français Paris
Stade Yves Du Manoir, Montpellier
Game on Sunday...
Date:Sunday, March 27
Previous result: Stade Français won 30-13 at home
Prediction: Based on the from book, there can be only one winner. Montpellier by ten points
Kick-off:21:00 (20.00 GMT)
Referee: Cyril Lafon
Castres Olympique 18-12 RC Toulon
Stade Pierre Antoine, Castres
On Friday, Toulon's play-off hopes took a step backwards when they went down 18-12 in a try-less encounter in Castres.
The showdown between the championship's top two place-kickers lived up to its billing as Castres full-back Romain Teulet and Toulon fly-half Jonny Wilkinson provided all the points from the tee.
Wilkinson added his fourth penalty of the evening with the very last kick of the game to save a losing bonus point for Toulon.