A lack of exposure in the Well Field at Pomeroy, County Tyrone, Northern Ireland, allowed previous researchers to work only from loose blocks in attempting to deduce an age for the Bardahessiagh Formation, occurring in the Palaeozoic inlier of Pomeroy. Brachiopods, collected in situ from a trench dug in the Well Field, during the summer of 1992, are being used to refine the age of the Bardahessiagh Formation. Three different assemblages are described. The assemblage collected from the top member of the Bardahessiagh Formation shows strong similarities with that of the Kirkcolm Formation, Kilbucho, Scotland, indicating a Woolstonian age. Faunas from the middle member and the top part of the lower member of the Bardahessiagh Formation comprise species of which oldest record has been found from rocks of Longvillian age in Laurentia.