Add to ORKGCold preamplifiers, designed in GaAs technology, are foreseen in the readout chain of the hadronic liquid argon end-cap calorimeter of the ATLAS experiment at LHC. The preamplifiers immersed in the liquid argon must withstand the hostile radiation environment during the operation of the LHC machine at the highest luminosities for the whole expected lifetime of the experiment. Preamplifiers, with a layout similar to the ones proposed, have been exposed to a high fluence of fast neutrons and to a high dose of #gamma# radiation. No significant deterioration of the performance has been observed for a neutron fluence up to #approx# 3.10"1"4 n cm"-"2 and up to 31 kGy, the highest #gamma# dose collected. Also only a moderate in...