The teams competing remained the same as the previous season with four Irish provinces; Munster, Leinster, Connacht and 2005–06 champions Ulster, three Scottish regions; Edinburgh, Border Reivers and Glasgow Warriors and four Welsh regions; Llanelli Scarlets, Cardiff Blues, Ospreys and Newport Gwent Dragons.

Prior to the season commencing it was announced by the Irish Rugby Football Union that some of their internationals were to be rested during part of the season as the Rugby World Cup takes place at the end.

[5] Major signings during the off-season include Justin Marshall for the Ospreys[6] and Stephen Jones for the Scarlets.

[8] Note: Flags to the left of player names indicate national team as has been defined under IRB eligibility rules, or primary nationality for players who have not yet earned international senior caps.

Television rights for the league are split between three broadcasters, BBC Wales, S4C and Setanta Sports.