Teimana Harrison's Northampton edged Bristol 32-26, despite a 21-point haul from fullback Jason Woodward. Mark Sorenson and Jack Lam saw action off the bench.
Sean Maitland's Saracens drew 13-all with Thomas Waldrom's Exeter.
Tane Takalua's Newcastle Falcons upset fourth-placed Bath 24-22. Making their first appearances for Bath were former Otago captain and loose forward Paul Grant and former Crusaders centre Robbie Fruean.
In a European Champions Cup catch-up game, rescheduled after the November death of Munster coach Anthony Foley, Munster convincingly defeated Racing-Metro 32-7 at Paris' Colombes stadium, where the home side had dropped just two of its last 26 games. Tyler Bleyendaal kicked five goals for the Irish province, while Rhys Marshall was a replacement, as was Francis Saili, in his long-awaited comeback. Dan Carter kicked a conversion for the Parisians. A feature of the Racing-Metro line-up was the debut of 2016 Counties Manukau loose forward So'otala Fa'aso'o, who made a good impression in the Mitre 10 Cup. Joe Rokocoko, Casey Laulala, Anthony Tuitavake, Chris Masoe and Ali Williams also played, meaning there were six former All Blacks in the home side's squad.
In the French Top 14, the Pau-Lyon fixture was postponed due to a frozen pitch.
La Rochelle continued their rise, beating Castres 22-8, anchored by a try to No 8 Victor Vito. Jason Eaton and Uini Atonio were alongside the loose forward in the pack. Former Chiefs and Steelers loose forward Maama Vaipulu debuted for Castres after a long injury layoff, alongside David Smith.
Rory Grice's Grenoble were narrowly beaten, 23-22, by Brive.
Simon Hickey kicked six goals, and copped a yellow card, in Bordeaux-Begles' 31-26 loss to Montpellier. Jayden Spence, Luke Braid and Hugh Chalmers all appeared for the former.
Toulouse, who fielded Luke McAlister, at first five, Joe Tekori, Carl Axtens and Census Johnston, beat Stade Francais 18-15 in Paris.
Clermont went clear at the top of the log with a decisive 30-6 win over Ma'a Nonu's Toulon. Isaia Toeava, Fritz Lee and Benson Stanley appeared for Les Jaunards.
In the Guinness PRO12, Connacht's troubles continued, losing 29-7 to Ospreys. Pat Lam's Kiwis were Tom McCartney, Jake Heenan and former prolific tryscoring Otago loose forward Naulia Dawai, while Ospreys had Ma'afu Fia, Brendon Leonard and Kieron Fonotia.
A try to lock Hayden Triggs helped Leinster hammer Zebre 70-6. Kurt Baker played at fullback for the Italians.
Scarlets, with Johnny McNicholl at fullback and Hadleigh Parkes at second five, beat Ulster 16-13, No 8 Sean Reidy conceding a yellow card.
Grayson Hart's Glasgow Warriors beat Cardiff Blues, who included Jarrad Hoeata, Rey Lee-Lo and Willis Halaholo, 29-15.
Nick Crosswell's Dragons defeated Dean Budd's Treviso 26-8.
The fifth round of the European Champions and Challenge Cups will be played this weekend.