Because of the unevenness of an 11 team league, Celtic Rugby introduce a scoring system whereby free weekends are acknowledged with a four point "win". The league season begins on 2 September 2005.

The league attendance record is smashed on five occasions throughout the season.

Ulster win the league title with a 19-17 victory against the Ospreys at Liberty Stadium on 26 May 2006 in the final weekend of the season, pipping Llanelli Scarlets by a single point.