Munster and Ulster have been handed difficult draws for the inaugural European Rugby Champions Cup.
Munster will play this season's Heineken Cup and English Premiership runners-up Saracens, French giants Clermont and Sale Sharks.
Ulster also have an imposing task in a group containing European champions Toulon, two-time winners Leicester and Pro12 rivals Scarlets.
RaboDirect Pro12 champions and three-time European kingpins Leinster will face Conor O'Shea's Harlequins, Castres and Wasps.
Ireland out-half Johnny Sexton's Racing Metro will battle Northampton, Ospreys and Benetton Treviso.
The draw for the revamped European competitions, which replace the old Heineken Cup and Amlin Challenge Cups, took place in Neuchatel, Switzerland this afternoon.
Twenty teams will take part in next season's competition, down from 24 in the Heineken Cup, seven from the English Premiership, six from the Top 14 and seven from the RaboDirect Pro12.
European Rugby Champions Cup draw
Pool 1: Saracens, Munster, Clermont Auvergne, Sale Sharks.
Pool 2: Leinster, Castres, Harlequins, London Wasps.
Pool 3: Toulon, Leicester Tigers, Ulster, Scarlets.
Pool 4: Glasgow Warriors, Montpellier, Bath, Toulouse.
Pool 5: Northampton Saints, Racing Metro, Ospreys, Benetton Treviso.
Trips to Castre, Dublin & .......... High Wycombe in next seasons European Rugby Champions Cup. Tough but exciting draw #ERCCPoolDraw— Mike Brown (@mikebrown_15) June 10, 2014
Connacht have been drawn in Pool 2 of the second-tier European Rugby Challenge Cup and will play Exeter Chiefs, Bayonne and La Rochelle.
European Rugby Challenge Cup draw
Pool 1: Cardiff Blues, London Irish, Grenoble, FIRA 1.
Pool 2: Exeter Chiefs, Bayonne, Connacht, La Rochelle.
Pool 3: Stade Français, Newport-Gwent Dragons, Newcastle, FIRA 2.
Pool 4: Edinburgh Rugby, Bordeaux-Bègles, London Welsh, Lyon.
Pool 5: Gloucester, Brive, Zebre, Oyonnax.