Clermont cruised to a 41-0 win over Biarritz in Round Nine of action in France while Bayonne, Toulon and Toulouse also claimed victories.
Bayonne 18-16 Perpignan
Clermont 41-0 Biarritz
Toulon 18-3 Brive
Toulouse 18-15 Stade Franšais
Agen 18-12 Montpellier
1. Clermont Auvergne 35
2. Toulouse 32
3. Castres 31
4. Toulon 28
5. Agen 24
6. Racing Metro 21
7. Perpignan 18
8. Brive 18
9. Stade Francais 16
10. Bayonne 15
11. Montpellier 14
12. Bordeaux-Begles 13
13. Lyon 12
14. Biarritz 10
Aviron Bayonnais 18-16 USA Perpignan
Stade Jean Dauger, Bayonne
Bayonne edged USA Perpignan to move above Bordeaux-Begles and Lyon, whose fixture was postponed after an outbreak of parotiditis, a salivary gland infection, at Lyon.
Bayonne, reinforced by the return of Cedric Heymans from World Cup duty with France, dominated Perpignan to lead 15-3 shortly after the break. The Catalans muscled their way back into contention but Bayonne held on to take the four points.
"I wanted to play today to help my teammates even if I only had one training session since coming back. I'm pleased we got the four points," said Heymans.
Clermont Auvergne 41-0 Biarritz Olympique
Parc des Sports Marcel Michelin, Clermont Ferrand
Australian fly-half Brock James contributed almost half the points in the mauling of bottom club Biarritz that put the defending champions back on top of the table.
They regained the summit from Castres, who had gone provisional top on Friday courtesy of their losing bonus-point despite having their seven-match winning run ended in a 23-19 defeat to Racing Metro.
Clermont followed up last week's 39-3 annihilation of Perpignan in style against struggling Biarritz, with James's third-minute try opening the floodgates.
Wesley Fofana added another shortly after and the French centre followed up again after the break with centre Gonzalo Canale and flanker Gerhard Vosloo also crossing for Clermont. James added three conversions and two penalties.
The only black cloud on an otherwise sunny day for the champions was the left knee injury suffered by French prop Thomas Domingo, meaning he faces a six month spell out.
Toulon 18-3 Brive
Stade Felix Mayol
Toulon moved fourth in the standings after beating Brive 18-3 at Stade Felix Mayol.
This was the perfect result for new coach Bernard Laporte on his first home match since taking over from Philippe Saint-Andre, who has replaced Marc Lievrement as France coach.
Suffering no ill effects from England's nightmare World Cup campaign in New Zealand, fly-half Jonny Wilkinson was responsible for all of Toulon's points with six penalties.
Stade Toulousain 18-15 Stade Franšais
Stadium de Toulouse
Toulouse overtook Castres for second spot with an 18-15 Top 14 defeat of the Parisians.
They won largely thanks to their second try, scored by Yves Donguy in the final 20 minutes to leave Stade Franšais still looking for their first points away from home this season.
SU Agen 18-12 Montpellier HR
Stade Armandie, Agen
In the late game, Montpellier's season failed to spark into life as they fell by six points.
All of the hosts points came via the boot of Conrad Barnard, who kicked six penalties while three tee efforts from Martin Bustos-Moyano and a Santiago Fernandez drop-goal saw the visitors leave with a losing bonus point.
What will add extra hurt to Montpol is the fact they were 0-6 up with fifteen minutes gone.