Castres took a step towards the Top 14 play-offs on Saturday thanks to a bonus-point win over Brive while Biarritz lost in Perpignan to be relegated.
Montpellier succeeded were most have failed by winning away to Oyonnax, who remain stuck in the relegation zone.
Elsewhere, Bordeaux-Bègles secured their place in the top flight thanks to a rare win in Bayonne.
Aviron Bayonnais 22-23 Union Bordeaux-Bègles
Stade Jean Dauger, Bayonne
A massive result for Bordeaux-Bègles, who claim their second win on the road this season and hand onto a chance of sneaking into the play-offs.
More importantly, it moves them clear of the threat of relegation. The same cannot be said for Bayonne, who face a nail-biting end to the season.
A huge defensive was at the origin of the positive result for UBB, who led 20-10 at half time and 23-10 on the hour mark but were made to hang on in the dying stages.
Tries: Rokocoko, O'Connor, Ugalde
Cons: Bustos Moyano, Ugalde
Pen: Bustos Moyano
Tries: Domvo, Madaule
Cons: Bernard 2
Pens: Bernard 3
Bayonne: 15 Scott Spedding, 14 Martin Bustos Moyano, 13 Joe Rokocoko, 12 Santiago Fernandez, 11 Marvin O'Connor, 10 Stephen Brett, 9 Mathieu Belie, 8 Dwayne Haare, 7 Julien Puricelli, 6 Jean Monribot, 5 Lisiate Faaoso, 4 Dewald Senekal, 3 Nemiah Tialata, 2 David Roumieu, 1 JC Janse van rensburg.
Replacements: 16 Anthony Etrillard, 17 Aretz Iguiniz, 18 Abdellatif Boutaty, 19 Jean Joseph Marmouyet, 20 Manu Ahotaeiloa, 21 Guillaume Rouet, 22 Matthieu Ugalde, 23 Gert Muller.
Bordeaux-Bègles: 15 Darly Domvo, 14 Metuisela Talebula, 13 Felix Le Bourhis, 12 Julien Rey, 11 Blair Connor, 10 Pierre Bernard, 9 Heini Adams, 8 Matthew Clarkin, 7 Hugh Chalmers, 6 Louis Madaule, 5 Adam Jaulhac, 4 Jandre Marais, 3 Albert Toetu, 2 Wayne Avei, 10 Pierre Bernard, 1 Jean-Batiste Poux,
Replacements: 16 Clement Maynadier 17 Jefferson Poirot 18 Alikisio Fakate 19 Matt Graham 20 Thibault Lacroix 21 Emmanuel Saubusse 22 Nicolas Sanchez 23 Salemane Sa
Referee: Romain Poite
Castres Olympique 38-6 CA Brive-Corrèze
Stade Pierre Antoine, Castres
A bonus-point win for Castres, but it didn't come easily as the home side battled to get past a Brive team that copped two yellow and two red cards.
Despite playing against 13 men for the last quarter, Castres had to wait until the bitter end for the dam wall to burst, scoring three tries in the last 12 minutes.
Castres led 16-3 at the break but the sparks flew after the restart as home prop Yannick Forestier saw red for kicking Damien Neveu while he was on the deck. Neveu also got his marching orders for retaliating.
The visitors were further reduced when Dominiko Waqaniburotu saw red for a very high tackle on Paul Bonnefond.
The win takes Castres up to fourth place.
Tries: Claassen, Grosso, Palis, Bonnefond
Cons: Kockott 2, Garcia
Pens: Kockott 4
Yellow cards: Peikrishvili
Pens: Germain 2
Yellow cards: Mela, Radikedike
Red cards: Neveu, Waqaniburotu
Castres: 15 Geoffrey Palis, 14 Max Evans, 13 Remi Lamerat, 12 Seremaia Bai, 11 Remy Grosso, 10 Daniel Kirkpatrick, 9 Rory Kockott, 8 Antonie Claassen, 7 Yannick Caballero, 6 Ibrahim Diarra, 5 Benjamin Desroche, 4 Rodrigo Capo ortega, 3 Karena Wihongi, 2 Mathieu Bonello, 1 Yannick Forestier.
Replacements: 16 Brice Mach, 17 Saimone Taumoepeau, 18 Piula Faasalele, 19 Jan Bornman, 20 Cedric Garcia, 21 Paul Bonnefond, 22 Brice Dulin, 23 Anton Peikrishvili.
Brive: 15 Gaetan Germain, 14 Guillaume Namy, 13 Arnaud Mignardi, 12 Thomas Sanchou, 11 Elia Radikedike, 10 Riaan Swanepoel, 9 Damien Neveu, 8 Kieran Murphy, 7 Dominiko Waqaniburotu, 6 Petrus Hauman, 5 Arnaud Mela, 4 Apisai Naikatini, 3 Johannes Coetzee, 2 Guillaume Ribes, 1 Karlen Asieshvili.
Replacements: 16 Francois da Ros, 17 Damien Lavergne, 18 Simon Pinet, 19 Said Hireche, 20 Jean baptiste Pejoine, 21 Romain Sola, 22 Andrew Mailei, 23 Patrick Barnard.
Referee: Laurent Cardona
US Oyonnax 8-22 Montpellier Hérault Rugby
Stade Charles Mathon, Oyonnax
Montpellier consolidated third place in the standings with a hard-fought win, in the snow!
Oyonnax now face an uphill battle to avoid relegation, despite having a game in hand as they must still travel to Perpignan and Brive and host Toulouse.
François Trinh-Duc was the star of the showing, kicking his team into a 15-3 lead by the hour mark before Timoci Nagusa sealed victory with a late try.
Silvere Tian's last-minute try was too little, too late for the home side,.
Pens: Trinh-Duc 4
Oyonnax: 15 Florian Denos, 14 Silvere Tian, 13 Pierre Aguillon, 12 Roimata Hansell pune, 11 Lucas Gonzalez Amorosino, 10 Benjamin Urdapilleta, 9 Agustin Figuerola, 8 Chad Slade, 7 Valentin Ursache, 6 Viliami Maafu, 5 Damian Browne, 4 Miroslav Nemecek, 3 Marc Clerc, 2 Jody Jenneker, 1 Antoine Tichit.
Replacements: 16 Neil graham Clark, 17 Clement Baiocco, 18 Damien Lagrange, 19 Nemia ratu Soqeta, 20 Christophe Andre, 21 Fabien Cibray, 22 Regis Lespinas, 23 Lukas Rapant.
Montpellier: 15 Pierre Berard, 14 Timoci Nagusa, 13 Anthony Tuitavake, 12 Wynand Olivier, 11 Lucas Dupont, 10 Francois Trinh-Duc, 9 Jonathan Pelissie, 8 Alex Tulou, 7 Paul Grant, 6 Alexandre Bias, 5 Thibaut Privat, 4 Robins Tchale Watchou, 3 Paea Faanunu, 2 Charles Geli, 1 Mikheil Nariashvili,
Replacements: 16 Thomas Bianchin, 17 Nahuel Lobo, 18 Sitaleki Timani, 19 Mamuka Gorgodze, 20 Benoit Paillaugue, 21 Jim Hamilton, 22 Benoit Sicart, 23 Yvan Watremez.
Referee: Jérôme Garcès
USA Perpignan 16-10 Biarritz Olympique
Stade Aimé Giral, Perpignan
Five-time champions and two-time European Cup runners-up Biarritz were relegated from the Top 14 on Saturday ending an 18-year stay in the elite division.
On Saturday they were holding on at 10-10 at the interval against Perpignan.
Welsh centre Aled Brew gave them a confidence-boosting edge with an 11th-minute try converted by Julien Peyrelongue, but Perpignan's English winger Richard Haughton scored a try on 20 minutes, converted by Welsh star James Hook.
Hook had already kicked an early penalty with Peyrelongue also knocking over an injury-time three points for 10-10 at the break.
However, Hook succeeded with two second-half penalties to give Perpignan victory and send Biarritz into the second division despite four more matches still to play.
Pens: Hook 3
Perpignan: 15 James Hook, 14 Joffrey Michel, 13 David Marty, 12 Sione Piukala, 11 Richard Haughton, 10 Tommaso Allan, 9 Nicolas Durand, 8 Daniel Leo, 7 Alasdair Strokosch, 6 Jean Pierre Perez, 5 Romain Taofifenua, 4 Guillaume Vilaceca, 3 Giorge Jgenti, 2 Guilhem Guirado, 1 Sona Taumalolo.
Replacements: 16 Romain Terrain, 17 Sebastien Taofifenua, 18 Sebastien Vahaamahina, 19 Justin Purll, 20 Dewaldt Duvenage, 21 Tommaso Benvenuti, 22 Lifeimi Mafi, 23 Kisi Pulu.
Biarritz: 15 Joe Pietersen, 14 Takudzwa Ngwenya, 13 Aled Brew, 12 Charles Gimenez, 11 Teddy Thomas, 10 Julien Peyrelongue, 9 Yann Lesgourgues, 8 Ueleni Fono, 7 Seremaia Burotu, 6 Tanguy Molcard, 5 Thibault Dubarry, 4 Erik Lund, 3 Benedict Broster, 2 Arnaud Heguy, 1 Thomas Synaeghel,
Replacements: 16 Johann Lourdelet, 17 Francisco Gomez Kodela, 18 Joshua Furno, 19 Eric Madeira, 20 Dimitri Yachvili, 21 Paul Couet lannes, 22 Benoit Guyot, 23 Eugene van Staden.
Referee: Cyril Lafon
FC Grenoble 13-26 Racing Métro 92
Stade des Alpes, Grenoble
Racing Métro comfortably put Grenoble away 26-13 during the final Top 14 clash of the weekend at Stade des Alpes on Saturday.
An early try from the hosts' loosehead, Albertus Buckle, converted by James Hart, handed Grenoble a seven-point lead.
But after Hart and Maxime Machenaud traded penalties, the Parisians came roaring back through Jamie Roberts, the British and Irish Lion carrying his powerful Six Nations form into the Métro midfield.
Machenaud converted, and the scrum-half added two further three-pointers before the break as the visitors took a 16-10 half-time lead.
And the big-spenders from the capital exerted their dominance after the interval, French international winger Marc Andreu crossing for a converted try, after Argentine Juan Martin Hernandez had boomed over a penalty.
A solitary strike from Hart was all the hosts had to show for a disappointing second forty.
Pens: Hart 2
Tries: Roberts, Andreu
Cons: Machenaud 2
Pens: Machenaud 3, Hernandez
Grenoble: 15 Fabien Gengenbacher, 14 Benjamin Thiery, 13 Rida Jaouher, 12 Geoffroy Messina, 11 Julien Caminati, 10 Blair Stewart, 9 James Hart, 8 Florian Faure, 7 Henry Vanderglas, 6 Fabien Alexandre, 5 Hendrik Roodt, 4 Benjamin Hand, 3 Richard Choirat, 2 Laurent Bouchet, 1 Albertus Buckle.
Replacements: 16 Kenan Mutapcic, 17 Anthony Hegarty, 18 Naude Beukes, 19 Jonathan Best, 20 Matthieu Nicolas, 21 Nigel Hunt, 22 Mathieu Loree, 23 Dayna Edwards.
Racing Métro : 15 Benjamin Lapeyre, 14 Adrien Plante, 13 Henry Chavancy, 12 Jamie Roberts, 11 Marc Andreu, 10 Juan Martin Hernandez, 9 Maxime Machenaud, 8 Jacques Cronje, 7 Bernard le Roux, 6 Wenceslas Lauret, 5 Francois van der Merwe, 4 Juandre Kruger, 3 Luc Ducalcon, 2 Dimitri Szarzewski, 1 Julien Brugnaut,
Replacements: 16 Virgile Lacombe, 17 Davit Khinchagishvili, 18 Karim Ghezal, 19 Antoine Battut, 20 Mike Phillips, 21 Fabrice Estebanez , 22 Benjamin Fall, 23 Brian Mujati.
Referee: Christophe Berdos