Saracens will open their European Rugby Champions Cup campaign by renewing hostilities with Clermont Auvergne, the French side they trounced to reach last term's Heineken Cup final.
The north London club will help launch an intriguing opening weekend for the inaugural European competition to replace the now-defunct Heineken Cup.
Clermont will be seeking revenge for their 46-6 defeat to Saracens in last term's European semi-final showdown at Twickenham.
Mark McCall's men - beaten Heineken Cup and Aviva Premiership finalists last season - will host Clermont on October 18.
Reigning European champions and French Top 14 winners Toulon will start their Pool Three battles by hosting Welsh region the Scarlets at Stade Mayol.
Current Premiership champions Northampton Saints will make the trip to Racing Metro in Pool Five when the 20th season of European competition gets under way.
Guinness PRO12 title holders Leinster will entertain Wasps in round one, the London club having qualified through the new play-off system at the end of last term.
Harlequins' Twickenham Stoop showdown with Castres on Friday, October 17 will kick-start the new season's European action.
Gloucester will open the European Rugby Challenge Cup proceedings by hosting Brive at Kingsholm on Thursday, October 16.
Italian sides Rovigo and Calvisano, Georgian outfit Tblisi Caucasians and Romanians Bucharest Wolves can all still win through to the new-look Challenge Cup.
The two-legged Challenge Cup Qualification Play-offs will be held next month, with Rovigo taking on Caucasians and Calvisano meeting Bucharest.