Last season's Grand Finalists Leinster condemned English side Saracens to their second successive defeat of the tournament winning the Pool 2 battle at Wembley.
A mammoth forward effort led by captain Jamie Heaslip made it two out of two in Europe for the Irish side after an opening weekend victory against Racing Metro.
Ireland play-maker Johnny Sexton scored all of the visitor's points, including a try in a 25-point haul.
On Friday evening Magners League Champions the Ospreys returned to winning ways with clinical performance against London Irish.
Tommy Bowe and Shane Williams both scored tries for the home side, with the Welsh winger touching down to round off a fantastic solo effort.
On the same evening Cardiff Blues fought back from a disappointing first half performance to claim a vital bonus point in France.
Castres Olympique led the way in the opening forty minutes, as they raced into a 27-6 half-time lead.
Dai Young's team talk at the break did the trick as the Blues dominated the second period and tries from Maama Molitika and Scott Andrews earned the region a vital away losing bonus point.
At Murrayfield Edinburgh came agonisingly close to beating former European Champions Northampton.
The home-side were at their creative best in the first forty minutes as Northampton struggled to stay in touch.
It was one-way traffic after an early Saints score as Allan Jacobsen, Netani Talei and Ben Cairns all rounded off stunning attacking moves.
It was Talei and second-row Fraser McKenzie who were at the heart of everything positive for Edinburgh who eventually went down 31-27.
In Pool 4 a spirited second-half performance from Aironi frustrated Bath in Northern Italy.
Bath raced into a 3-17 lead but the Italian side dug deep and created a lot out-wide after the break, but failed to cross the whitewash.
Aironi, who are back in Magners League action away to the Dragons on Friday evening got their only points of the afternoon through two Ludovic Mercier penalties.
The Italian's opponents this weekend the Dragons suffered their second defeat of the tournament at the hands of the European Champions Toulouse.
In a tight first half the Dragons took the game to the French side and trailed by just six points of the break. A comprehensive second period by Toulouse earned them the victory in South Wales.
After their heroic performance against Leicester last weekend, Benetton Treviso travelled to Perpignan and looked on course for their second successive victory at Stade Aime Giral until a late surge from the home side.
19-year-old centre Tommaso Benvenuti scored a brace for the second time in two weeks to once again earn high-praise.
Glasgow impressed in an entertaining game at Adams Park against London Wasps but ended up going down 38-26.
Ruaridh Jackson scored 21 points including a try for the visitors, with Dougie Hall crossing for Glasgow's second try.
Ulster suffered a 35-15 defeats at the hands of last season's European Cup finalists Biarritz.
Andrew Trimble and Rory Best both scored in the South of France with Ruan Pienaar adding five-points with the boot.
The Scarlets went down 46-10 in Pool 5 to English Champions Leicester Tigers. The Welsh side impressed during the opening half with Morgan Stoddart crossing for a try, Stephen Jones converted and added a penalty to take the Scarlets into the break 13-10 down.
The Tigers struck quickly in the second-half to take victory.
In the Amlin Challenge Cup, Connacht got their campaign back on track - beating Bayonne 16-13 at the Sportsground.
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