Paris - Four-time champions Toulouse cruised past two-time winners Leicester 23-9 in the torrential rain of south-west France on Sunday in a battle of European Cup heavyweights.
The win could prove crucial in a Pool 2 which also includes powerful 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 Toulouse flexed their muscles.
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 Mallender.
"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."
Results from the first round of European Cup matches on Sunday:
Toulouse (FRA) 23 Leicester (ENG) 9
Northampton (ENG) 24 Glasgow (SCO) 15
Sale (ENG) 34 Cardiff Blues (WAL) 33
Toulon (FRA) v Montpellier (ENG) (19:00)
Edinburgh (SCO) 0 Saracens (ENG) 45
Racing Metro (FRA) 22 Munster (IRL) 17
Zebre (ITA) 10 Connacht (IRL) 19
Harlequins (ENG) 40 Biarritz (FRA) 13
Clermont (FRA) 49 Scarlets (WAL) 16
Leinster (IRL) 9 Exeter (ENG) 6
Ospreys (WAL) 38 Treviso (ITA) 17
Ulster (IRL) 41 Castres (FRA) 17
2nd rd: October 17-20
3rd rd: December 6-9
4th rd: December 13-16
5th rd: January 10-13, 2013
6th rd: January 17-20
Quarter-finals: April 4-7
Semi-finals: April 26-28
Final: May 18 at Dublin