The ISEQ index of Irish shares closed down 78.39 points to 2,366.13, a drop of 3.21%.
The fall reflected the trend in global markets amid ongoing concerns over the US economy and the eurozone debt crisis.
Among the fallers, Merrion Pharmaceutical fell 15c to €0.50, a drop of 23.08%.
Kenmare Resources was down 6c to €0.45; Aer Lingus fell 4c to €0.63 and Smurfit Kappa closed down 30c to €4.50.
Also in the red were CRH, closing down 65c to €10.52; Glanbia, shedding 24c to €4.35; Tullow Oil 78c off at €14.42, and FBD, down 30c to €6.10.