Whereas the competition previously featured teams from the lower levels of the English rugby pyramid, this season it was contested by the 12 teams from the English Premiership and the four Welsh regional sides from the Celtic League.

The competition began with a pool stage, in which each pool consisted of a Welsh region and three English sides, with each team playing the others in the group once.

Pool matches were played in September, October and December 2005.

The team that finished top of each pool advanced to the semi-finals.

The semi-finals were played at the Millennium Stadium in Cardiff on 4 March 2006, and the final was played at Twickenham Stadium in London on 9 April.