In that first season Division 1 was made up of Ballymena, Cork Constitution, Garryowen, Instonians, Lansdowne, Malone, St. Mary's College, Shannon and Wanderers.
Division 1 was dominated by Munster clubs for the first decade with Shannon winning four titles in a row between 1995 and 1998. St. Mary's College were the first non Munster club to lift the trophy when they won in the 1999/00 season and were followed by Dungannon in 2000/01.
Ulster Bank, Community Rugby partner of the IRFU, sponsor the league
Shannon (9), Cork Constitution (4), Garryowen (3), St. Mary's College (2), Lansdowne (2), Clontarf (2), Young Munster (1), Dungannon (1), Ballymena (1), Old Belvedere (1).
In the 1997/98 season a top four playoff was introduced for the first time. The playoffs were replaced with a straight league in the 2011/12 season but re-introduced for 2014/15.
|1992/93||Young Munster||Cork Constitution|
|1999/00||St. Mary's College||Lansdowne|
|2009/10||Cork Constitution||St. Mary's College|
|2010/11||Old Belvedere||Cork Constitution|
|2011/12*||St. Mary's College||Clontarf|