Paris - English Premiership club Northampton, European champions in 2000, got this season's Cup campaign off to a flying start with a 18-14 win over Castres on Friday.
Tries from England back Ben Foden and ex-All Black Bruce Reihana, allied with penalties from Stephen Myler and Shane Geraghty were enough to see off the French outfit, who dominated much of the game and return home with a defensive bonus point.
Joe Tekori crossed the whitewash for Castres, with Pierre Bernard nailing two penalties and Kiwi outside-half Cameron McIntyre kicking a drop-goal.
Castres' Scotland international lock Scott Murray said his team's display was something to be proud of.
"We sometimes were lacking come the final pass," Murray said. "But we played with lots of passion.
"The coach asked us to show our hearts and what we were capable of doing.
"It's sometimes said that French teams don't play well away but we proved the opposite."
Pool 1 rivals Cardiff Blues, winners of last season's European Challenge Cup, play Edinburgh on Saturday.
At Ravenhill, Springbok scrum-half Ruan Pienaar scored a try on his debut in the competition as Ulster sealed a bonus-point 30-6 victory over newly-formed Italian outfit Aironi.
Pienaar, who also kicked two penalties, was one of four try scorers for the Irish province along with Andrew Trimble, Ian Humphreys and Simon Danielli.
The Springbok's five-pointer sealed a satisfying evening's work for Ulster, earning them a bonus win point ahead of what promises to be a tougher Pool 4 match against Biarritz next weekend.
In Pool 6, which also includes defending champions Toulouse and Wasps, Glasgow ground out a 21-13 win over Newport Gwent Dragons.
Tries from Graeme Morrison and Fergus Thomson sealed the win for the home side and although they had some shaky spells, their pace behind the scrum always had the visitors in trouble.
Heineken Cup round one results on Friday.
Pool 1
Northampton 18 Castres 14
Pool 4
Ulster 30 Aironi Rugby 6
Pool 6
Glasgow 21 Newport Gwent Dragons 13
Playing on Saturday
Pool 1
Cardiff Blues v Edinburgh
Pool 2
Leinster v Racing Metro
Clermont Auvergne v Saracens
Pool 3
Toulon v Ospreys
London Irish v Munster
Pool 5
Treviso v Leicester
Llanelli v Perpignan
Playing on Sunday
Pool 4
Bath v Biarritz
Pool 6
Toulouse v Wasps