Reigning Amlin Challenge Cup champions, and three-time Heineken Cup winners, Leinster Rugby, remain at the top of the ERC European rankings, and they are joined in Tier 1 by Toulon, Clermont, Toulouse, Munster Rugby and Ulster Rugby.
Cardiff Blues appear in Tier 2 along with Northampton Saints, Harlequins, Saracens, Leicester Tigers and Perpignan .
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 France, as there are seven French clubs in next season's tournament.
2013/14 Heineken Cup clubs and tiers
Tier 1- Leinster Rugby, Toulon, Toulouse, ASM Clermont Auvergne, Ulster Rugby, Munster Rugby
Tier 2- Northampton Saints, Harlequins, Cardiff Blues, Saracens, Leicester Tigers, Perpignan
Tier 3- Edinburgh Rugby, Ospreys, Scarlets, Glasgow Warriors, Montpellier, Connacht Rugby
Tier 4- Gloucester Rugby, Castres Olympique, Racing Metro 92, Exeter Chiefs, Benetton Treviso, Zebre