We report an investigation of the degradation caused by ionizing radiation exposure and Fowler-Nordheim current injection in MOS capacitors with rapid thermally nitrided thin-gate oxides. The effect of nitridation conditions on the extent of the degradation was studied. It was observed that the damage caused by ionizing radiation and constant-current stressing are strongly dependent on the nitridation temperature and duration. Also, this dependence is different for the two cases. These observations are explained using some defect generation models and structural changes in oxide due to nitridation.