Cardiff Blues and Biarritz Olympique, both former Heineken Cup finalists, complete the top group of six.
Once the Tier 1 clubs have each been allocated a different Pool no club from the same Tier will be drawn in the same Pool and no Pool will have more than one club from the same country with the exception of England, as there are seven English teams.
The draw will launch the countdown to a tournament which will climax at Twickenham Stadium on the weekend of 19 / 20 May, 2012, with the 17th Heineken Cup final.
CLUBS AND TIERS
TIER 1 - Leinster, Toulouse, Munster, Cardiff Blues, Biarritz Olympique, Leicester Tigers
TIER 2 - Northampton Saints, ASM Clermont Auvergne, Ospreys, Bath Rugby, Harlequins, London Irish
TIER 3 - Ulster Rugby, Saracens, Gloucester Rugby, Glasgow Warriors, Scarlets, Edinburgh
TIER 4 - Connacht Rugby, Benetton Treviso, Castres Olympique, Montpellier, Racing Metro 92, Aironi Rugby