Former Heineken Cup champions Toulouse powered to a 23-9 victory over Leicester Tigers at a wet and rainy Stade Ernest Wallon in France.
Toulouse winger Gael Fickou scored the only try of the match in the first half and the French side kept Leicester tryless.
Former All Black Luke McAlister missed the conversion of Fickou's try but went on to score eighteen of Toulouse's 23 points through six penalties.
The win could prove crucial in a Pool 2 which also includes Welsh side Ospreys who had opened their campaign with a bonus point 38-17 win over Treviso on Saturday.
Toby Flood had kicked Leicester 9-6 ahead by the 35th minute with three penalties to a brace from former All Black Luke McAlister to briefly give the English side hope of repeating Harlequins' shock win at Toulouse last season.
But the game turned on a fine individual try by highly-rated centre Gael Fickou just before the interval.
Leicester's Thomas Waldrom lost the ball at the halfway line, 18-year-old Fickou kicked ahead, outsprinting his pursuers to score what was the only try of the game much to the delight of the 38,000 crowd.
McAlister missed the conversion but went on to kick four second-half penalties as the four-time champions Toulouse flexed their muscles.
"With the rain falling heavily, it was a really difficult match," said Toulouse coach Guy Noves.
"It was tough so I can only congratulate my players for rolling up their sleeves although it was unfortunate that we didn't score one or two more tries and kill off the opposition."
Leicester coach Richard Cockerill admitted his side had paid the price for not hammering home their advantage when they were ahead.
"We controlled the match for 38 minutes when we kept up a three-point lead and we wanted to take the match in hand," he said.
"But we weren't able to do it for more than the first half and we have to be better than that. We didn't do it and we were punished for it."
Earlier Sunday, Northampton clawed back 15 unanswered points to defeat Glasgow 24-15 in Pool 4 as Sale trumped Cardiff Blues in a 34-33 Pool 6 thriller.
Glasgow roared into a 15-point lead thanks to tries by Josh Strauss and Sean Lamont, Peter Horne nailing a penalty and conversion.
But Saints' stand-out Samoan centre George Pisi hit back with two tries, one converted by Stephen Myler, to make it 15-12 to the visitors at the break.
Myler then crossed for a try minutes after the break and Russian winger Vasily Artemyev also touched down to ensure a bonus-point victory for Northampton, European champions back in 2000.
"We were under a bit of pressure, but what was pleasing was the way we came back and kept our composure. In the second half, we controlled the game," said Saints coach Jim Mallinder.
"I think we are in decent shape. When we are on top of our game we are a hard side to beat, and we need to keep at that intensity every single week."
In Salford, Sale left it late in beating Cardiff Blues, for whom Wales wing Alex Cuthbert scored a hat-trick, all converted by full-back Leigh Halfpenny who also notched up four penalties.
However, that haul was not enough as Sale, whose league form has so far this season been woeful, launched a comeback inspired by a Danny Cipriani try with 25 minutes remaining.
Mark Jennings and Tony Buckley also crossed the whitewash and, allied with 12 points from Nicky MacLeod's boot and Rob Miller providing a crucial penalty and two conversions at the death, Sale grabbed an unlikely yet vital victory.
"It's something we've been longing for," said Cipriani, whose Sale team went into the game having lost five matches in succession.
"We had to give the fans something to cheer about and we did."
Final Score Toulouse 23 (11) Leicester 9 (9)
Penalties: McAlister 6
Penalties: Flood 3
Referee: Nigel Owens (Wales)
Clement Poitrenaud, Vincent Clerc, Florian Fritz, Gael Fickou, Yoann Huget, Luke McAlister, Jean Marc Doussain; Gurthro Steenkamp, Gary Botha, Census Johnston, Romain Millo-Chluski, Yoann Maestri, Yannick Nyanga, Thierry Dusautoir (capt), Louis Picamoles.
Replacements: Christopher Tolofua, Jean-Baptiste Poux, Antoine Guillamon, Patricio Albacete, Jean Bouilhou, Yannick Jauzion, Luke Burgess, Timoci Matanavou.
Scott Hamilton, Niall Morris, Manu Tuilagi, Anthony Allen, Vereniki Goneva, Toby Flood, Ben Youngs; Logovi'i Mulipola, Tom Youngs, Dan Cole, Graham Kitchener, Geoff Parling, Steve Mafi, Thomas Waldrom, Jordan Crane (capt).
Replacements: George Chuter, Marcos Ivan Ayerza, Martin Castrogiovanni, Ed Slater, Richard Thorpe, Sam Harrison, George Ford, Matt Smith