London Wasps saw off a stiff challenge from Racing Metro 92 on Sunday, whilst Saracens secured a bonus-point win over Rovigo.
Dave Walder was the hero for Wasps as they got their Amlin Challenge Cup campaign off to a successful start at Adams Park.
But it was an often testing afternoon for the twice Heineken Cup winners against wealthy Paris club Racing-Metro 92.
Former Newcastle fly-half Walder kicked all his team's points to edge a tense Pool Four encounter.
Walder, who can expect an extended run in the number 10 shirt with Danny Cipriani facing six weeks out injured, slotted three penalties in each half for an 18-13 verdict.
Wasps trailed by a point at half-time, conceding the game's solitary try to Racing-Metro flanker Ashley Clarke, but Walder kept his cool and secured an all-important home win.
The French club included star signing, South African World Cup winner Francois Steyn, who kicked a penalty, while substitute Julien Saubade also slotted a penalty and fly-half Jonathan Wisniewski converted Clarke's touchdown.
A losing bonus point could be important in the final shake-up for Racing, especially as only the five pool winners are guaranteed quarter-final places.
Unbeaten Guinness Premiership leaders Saracens made it six successive wins in all competitions this season by seeing off Pool Three opponents Rovigo 36-12 at Vicarage Road.
Fly-half Jake Sharp marked his full debut with an assured display as Saracens eased to victory without hitting top gear.
The 18-year-old slotted three penalties, a drop-goal and conversion, while Derick Hougaard also added a conversion in Saracens' bonus point success.
Kevin Sorrell, Don Barrell, Michael Horak and Rodd Penney scored tries for the home side, who can expect a far tougher Pool Three test when they tackle Jonny Wilkinson's Toulon at Stade Felix-Mayol next Thursday night.