Exeter Chiefs will face the defending Heineken Cup champions for the second successive season after they were drawn with Toulon.
The Chiefs, who made their debut in the competition last year against then champions Leinster, will face the powerful French side in Pool 2, as well as Cardiff Blues and Glasgow Warriors.
There are some mouth-watering match-ups, such as in Pool 1, where Amlin champions Leinster will meet Top 14 winners Castres, Northampton Saints and the Ospreys.
Pool 4 will also be fiercely contested, with runners-up Clermont Auvergne paired with Harlequins and a Racing Metro side that have bolstered their ranks with the likes of Lions pair Jonathan Sexton and Jamie Roberts.
Toulouse and Connacht have been drawn together for the second time in three years, with last year's semi-finalists Saracens and Zebre completing Pool 3, while in Pool 5 Premiership champions Leicester face daunting trips to Ulster and Montpellier.
Munster and Perpignan are the frontrunners to emerge from the final pool, but will face stern challenges from both Gloucester and Edinburgh.
Pool 1: Leinster, Northampton, Ospreys, Castres.
Pool 2: Toulon, Cardiff, Glasgow, Exeter.
Pool 3: Toulouse, Saracens, Connacht, Zebre.
Pool 4: Clermont Auvergne, Harlequins, Scarlets, Racing Metro.
Pool 5: Ulster, Leicester, Montpellier, Treviso.
Pool 6: Munster, Perpignan, Edinburgh, Gloucester.